Voice Communication System Procurement Guidelines

EUROCONTROL

Voice Communication System

Procurement Guidelines

TITLE

Voice Communication System Procurement Guidelines

EATMP Infocentre Reference: 03052701

Document Identifier Edition Number: 1.0

VCS Procurement Guidelines.doc Edition Date: 22.05.2003

Abstract

This document offers guidance to ECAC Member States who wish to procure Voice Communication Systems that will be compatible at both the Operational and Engineering levels with the Eurocontrol Air Traffic Management Strategy For The Years 2000 +.

Keywords

VCS VCS-TF COMT Voice

Communication Procurement Guidelines Ground Telephone

Air-Ground Telephony Radio PBX

QSIG ATS-QSIG ATS-R2 ATS No.5

Contact Person(s) Tel Unit

Chris Clegg +32 2

7293356

CSM Business Unit

STATUS, AUDIENCE AND ACCESSIBILITY

Status Intended for Accessible via

Working Draft o General Public þ Intranet þ

Draft o EATMP Stakeholders o Extranet o

Proposed Issue o Restricted Audience o Internet (www.eurocontrol.int) þ Released Issue þ Printed & electronic copies of the document can be obtained from

the EATMP Infocentre (see page iii)

EUROCONTROL Headquarters 96 Rue de la Fusée B-1130 BRUSSELS Tel: +32 (0)2 729 51 51 Fax: +32 (0)2 729 99 84 E-mail: [email protected]

Open on 08:00 - 15:00 UTC from Monday to Thursday, incl.

DOCUMENT APPROVAL

The following table identifies all management authorities that have successively approved the present issue of this document.

AUTHORITY

NAME AND SIGNATURE

DATE

Please make sure that the EATMP Infocentre Reference is present on page ii.

VCS - Task Force

Chairman _{Chris Clegg}

Head of Business

CSM _{Mel Rees}

Acting Director

DOCUMENT CHANGE RECORD

The following table records the complete history of the successive editions of the present document. EDITION NUMBER EDITION DATE INFOCENTRE

REFERENCE REASON FOR CHANGE

PAGES AFFECTED

CONTENTS

PART 1 - INTRODUCTION... 14

1. SCOPE OF DOCUMENT ... 14

2. SCOPE OF THESE PROCUREMENT GUIDELINES ... 14

3. ENQUIRIES AND COMMENTS ... 14

PART 2 - VOICE COMMUNICATION SYSTEM IN OUTLINE... 18

1. GROUND TELEPHONE ... 18

1.1 HUMAN-MACHINE INTERFACE (HMI) ... 18

1.2 MAIN SWITCH... 18

1.3 INTERNAL INTERFACES... 19

1.4 EXTERNAL INTERFACES... 19

1.5 SYSTEM MANAGEMENT / ENGINEERING TERMINAL... 19

1.6 SYSTEM CONFIGURATION... 19

2. AIR-GROUND RADIO ... 20

2.1 HUMAN-MACHINE INTERFACE (HMI) ... 20

2.2 MAIN SWITCH... 20

2.3 INTERNAL INTERFACES... 21

2.4 EXTERNAL INTERFACES... 21

2.5 SYSTEM MANAGEMENT / ENGINEERING TERMINAL... 21

2.6 SYSTEM CONFIGURATION... 21

3. COMBINED GROUND TELEPHONE AND AIR-GROUND RADIO VCS ... 22

PART 3 - USER FACILITIES... 24

1. GROUND TELEPHONE ... 24

1.1 PRIMARY USER GROUND TELEPHONE FACILITIES... 24

1.2 DEFINITIONS AND ASSUMPTIONS... 24

1.3 ACCESS METHODS... 26

1.3.1 Direct Access... 26

1.3.2 Instantaneous Access... 27

1.3.3 Indirect Access ... 29

1.3.3.1 Call Queuing facility ... 29

1.4 CALL PRIORITY... 31

1.4.1 Intrusion by a Priority Call ... 32

1.5 SIMULTANEOUS CALLS... 32

1.6 SUPPLEMENTARY USER TELEPHONE FACILITIES... 33

2.2.1 Basic Description ... 39

2.2.2 Modes of Operation... 40

2.2.3 Receiving - frequency active ... 40

2.2.4 Audio Device Selection – Rx Mode ... 40

2.2.5 Transmitting ... 41

2.2.6 Side Tone... 41

2.2.7 Multiple Frequencies... 41

2.2.8 Transmitter / Receiver Selection ... 41

2.2.9 Main and Standby Radio Coverage... 42

2.2.10 Frequency Cross-Coupling ... 42

2.2.11 Use of Optional Channels... 43

2.2.12 Short-Term Recording ... 43

PART 4 - HUMAN-MACHINE INTERFACE (HMI)... 46

1. GENERAL ... 46

1.1 ACTIVATION AND PRESENTATION DEVICES... 46

1.2 AUDIO DEVICES... 47

1.3 MANAGEMENT OF MIXED AIR-GROUND RADIO AND GROUND TELEPHONE COMMUNICATIONS... 48

1.4 TRAINING FACILITIES... 49

1.4.1 Monitoring ... 49

1.4.2 Student / Mentor Facility... 49

1.5 HUMAN ENGINEERING GUIDELINES... 49

1.6 PHYSICAL ENVIRONMENTAL CONSIDERATIONS... 51

PART 5 – ENGINEERING GUIDELINES ... 54

1. ENGINEERING GUIDELINES ... 54

1.1 AVAILABILITY, RELIABILITY AND MAINTAINABILITY (ARM)... 54

1.1.1 Availability ... 54

1.1.2 Reliability ... 55

1.1.2.1 Reliability and System Redundancy ... 55

1.1.3 Maintainability... 56

1.1.3.1 Hardware ... 56

1.1.3.2 Software ... 56

1.2 GENERAL RESPONSE CRITERIA... 57

1.2.1 Call Processing Delay... 57

1.2.2 PTT Set-Up Delay ... 57

1.2.3 A/C call (Squelch) Delay... 58

1.2.4 Dial Tone Delay ... 58

1.2.5 Software response delay... 58

1.2.5.1 Alarm Indications ... 58

1.2.5.2 Configuration Changes ... 58

1.2.6 System Response Times ... 59

1.2.7 Performance Conditions ... 59

1.2.8 Software ... 59

1.3 TRAFFIC HANDLING CAPACITY AND BLOCKING... 60

1.3.1 Traffic Handling... 60

1.3.2 General Guidance on Non-Blocking Functionality... 60

1.3.3 PTT and A/C call Blocking... 61

1.4 SYSTEM MANAGEMENT... 61

1.4.1 Performance management... 61

1.4.2 Fault (or maintenance) management ... 62

1.4.3 Configuration management... 62

1.4.5.2 System security... 67

1.4.5.3 Public Network security ... 67

1.5 MODULARITY... 67

1.5.1 General guidelines ... 67

1.5.2 System Modularity for Security ... 67

1.6 ACCESSIBILITY... 68

1.7 SAFETY AND PROTECTION... 68

1.8 ELECTROMAGNETIC COMPATIBILITY (EMC)... 68

1.9 SYNCHRONISATION STRATEGY... 68

1.10 LINE INTERFACES... 69

1.10.1 General ... 69

1.10.2 Legacy Interfaces... 69

1.10.3 Public network interfaces ... 70

1.10.4 Inter-VCS Circuit Interfaces ... 71

1.10.4.1 Analogue Signalling Systems ATS-R2, ATS-No5 ... 71

1.10.4.2 Digital Signalling System EN 301 846 "ATS-QSIG”... 71

1.11 NUMBERING SCHEMES... 72

1.12 STANDBY VCS REQUIREMENTS... 72

1.13 CALL AND EVENT RECORDING... 73

1.13.1 Radio and Telephone voice recording ... 73

1.13.2 Telephone Call event recording... 73

1.13.2.1 Outgoing call information ... 74

1.13.2.2 Incoming call information ... 74

1.13.3 Radio Call event recording... 75

1.13.3.1 Outgoing call information ... 76

1.13.3.2 Incoming call information ... 76

1.13.3.3 Best Signal Selection... 76

2. CONNECTION APPROVALS REQUIREMENTS ... 77

3. TRAINING ... 77

4. DOCUMENTATION ... 77

ANNEX A – REFERENCES... 79

ANNEX B – ABBREVIATIONS ... 81

ANNEX C - REF MODEL EXAMPLE FOR THE MANAGEMENT OF INCOMING CALLS ... 83

C.1 INTRODUCTION... 83

C.1.1 IDA Call Queue... 84

C.1.2 The DA Panel ... 84

EXECUTIVE SUMMARY

This document offers guidance to ECAC Member States who wish to procure Voice Communication Systems that will be compatible at both the Operational and Engineering levels with the ATM Strategy For The Years 2000+ [1].

The emphasis is on Ground Telephone aspects where the User Facilities are described in detail along with the Engineering requirements necessary to support them. Air-Ground aspects are also covered but to a much less extent than those for the Ground Telephone. In compiling these guidelines due regard has also been paid to work completed within ICAO to revise related parts of Annex 10 [7]. Thus VCSs specified in accordance with these guidelines should also have a high degree of compatibility with related ICAO Recommendations as well as those of Eurocontrol.

Wherever possible the Features and other implementation aspects have been left open so as not to prevent VCS suppliers from offering innovative solutions.

PART 1

PART 1 - INTRODUCTION

1.

SCOPE OF DOCUMENT

This document has been produced by the Voice Communications System Task Force (VCS-TF) convened by the Communications Team (COMT) of Eurocontrol. The purpose of the document, as its title implies, is to offer selective guidance to ECAC Member States in compiling a procurement specification for a Voice Communications System (VCS).

The guidance is "selective" because it is only intended to address those matters that contribute towards a VCS being compatible, at both User/Operational and Engineering levels, with other VCSs both in neighbouring as well as distant States. It would thus be possible for all VCSs, that have been specified in accordance with these guidelines, to become part of an ECAC-wide voice telephone network, the justification for which is to provide voice communications systems in support of the Strategy for ATM in the Years 2000+ [1] and in accordance with the associated Communications Strategy [2]. Accordingly these guidelines do not constitute a complete and comprehensive VCS specification, which it is assumed, will be written by experienced Operational and Engineering experts. If preferred States may also request the assistance of Eurocontrol.

Equally the Guidelines do not include any contractual procedures and endeavours to avoid the use of any terms or system descriptions that may be regarded as proprietary to a particular manufacturer. The objective is not to stifle innovation by manufacturers thus opening up the possibility of a number of VCSs products in a free market that may meet a particular customer's requirements.

2.

SCOPE OF THESE PROCUREMENT GUIDELINES

These Procurement Guidelines have been written to cover both Ground Telephone and Air-Ground Radio aspects. The emphasis, however, is on the Ground Telephone parts. For confirmation of the current status of these Guidelines please refer to Eurocontrol as detailed in Part 1: section 3 following.

3. ENQUIRIES

AND

COMMENTS

Comments on this document are welcome and should be directed towards Eurocontrol as detailed below. Eurocontrol would also be pleased to provide answers to any enquiries that may arise.

Eurocontrol

Rue de la Fusee, 96 B-1130 Brussels Belgium

For the attention of the CSM Business Division Tel ++ 32 2 729 3291

PART 2

PART 2 - VOICE COMMUNICATION SYSTEM IN OUTLINE

A Voice Communication System (VCS) may be comprised of two major components – Ground Telephone and Air-Ground Radio; each of these is described, in outline, below.

1. GROUND

TELEPHONE

The Ground Telephone component of a VCS permits telephone conversations to take place between Users (for a description of 'User' see Part 3: Section 1.2) connected to the same VCS or to other external Users. In many respects the everyday equivalent of a Ground Telephone VCS is the Private Branch Exchange (PBX) where many Users are able to call each other or to make long distance calls via the Public Switched Telephone Network (PSTN) or private circuits. In some cases a commercially available PBX may be all that is required for a particular application but the special attributes of a VCS designed and manufactured for ATM applications usually preclude this. Although the switching capabilities of a PBX and a VCS are almost identical, most commercially available PBX systems do not provide the functionality required at a Controller Working Position (CWP).

The Ground Telephone component may be further considered to consist of five sub-systems:

· Human-Machine Interface (HMI) · Main Switch

· Internal Interfaces · External Interfaces

· System Management / Engineering Terminal

1.1

Human-Machine Interface (HMI)

The HMI requirements are further described in Part 4: section 1, but it is essentially the part that permits a User to make and receive telephone calls. Everyday examples include Ordinary Telephones, Feature-phones, Key-Pads and Attendant Consoles – each of these have an increasing level of User Facilities and complexity. The HMI requirements are usually so specialised for ATM that off-the-shelf commercial PBX products will not meet them.

1.2 Main

Switch

This is the principal component of the system and contains all the switching hardware and software together with the interfaces to the HMI and interfaces to the outside

The Availability, Reliability and Maintainability (ARM) requirements of the main switch (and all component parts) are addressed in Part 5: section 1.1 and these usually exceed those of off-the-shelf commercial PBX products.

1.3 Internal

Interfaces

Internal Interfaces connect the main switch to the HMI. Depending upon the multiplicity of HMIs required, several types of Internal Interface may be required. Although Internal Interfaces may be physically part of the Main Switch it is useful to regard them as separate components because they often contain special software or firmware that is independent of the main switch and control system

1.4 External

Interfaces

External Interfaces connect the main switch to the outside world and may be of digital, or analogue (exceptionally DC) types. Although External Interfaces may be physically part of the Main Switch it is useful to regard them as separate components because they often contain special software or firmware that is independent of the main switch and control system. (Further Engineering information on Ground Telephone External Interfaces is given in Part 5: section 1.10).

1.5

System Management / Engineering Terminal

A System Management / Engineering Terminal can provide a multitude of facilities ranging from the configuration of an HMI through to the collection of system performance parameters. It is common for such terminals to be PC-based systems with sophisticated software to provide a user-friendly interface in order to carry out either tedious or complex tasks. (Further information on System Management / Engineering Terminals is given in Part 5: section 1.4).

1.6 System

Configuration

Having described the component parts of the Ground Telephone VCS as five subsystems above, there is no reason why (with the possible exception of the System Management / Engineering Terminal) such a system may not be supplied as a single unit including all components; such systems are often purchased either for very small operational units or as standby/back-up systems for large operational units as further described in Part 5: section 1.12.

2. AIR-GROUND

RADIO

The Air-Ground Radio component of a VCS permits radio telephone conversations to take place between Users connected to the VCS and to mobile units – primarily aircraft but also to ground mobiles too. In many respects the everyday equivalent of an Air-Ground Radio VCS is a radio control system that may be used by the emergency services (fire, police, ambulance and coastguard in particular). Radio applications are generally considered to be much more safety critical than those of Ground Telephone and accordingly the ARM criteria are much more stringent. The basic functionality is for a controller to be able to select one or more radio frequencies and then to be able to transmit to and receive messages from pilots of aircraft.

The use of Headsets for this type of application is often common.

In a similar manner to the Ground Telephone Component, the Air-Ground Radio component of a VCS may be further considered to consist of five sub-systems:

· Human-Machine Interface (HMI) · Main Switch

· Internal Interfaces · External Interfaces

· System Management / Engineering Terminal

2.1

Human-Machine Interface (HMI)

The HMI subsystem essentially permits a User to select frequencies and to be able to either monitor them or to make transmissions on them – usually both. A headset is a common audio device but many users prefer hand microphones and loudspeakers or handsets; a VCS should be able to accommodate all of these to meet any User preferences or operational requirements.Some form of control panel is also provided to select frequencies and to be able to see which frequency is active. Due to the individual requirements and preferences by ANSPs these guidelines do not include any specific details of HMI attributes or standards.

2.2 Main

Switch

This is the principal component of the system and contains all the switching hardware and software together with the interfaces to the HMI and interfaces to the transmitter and receiver equipment. Power supplies for all systems are also usually included here.

2.3 Internal

Interfaces

Internal Interfaces connect the main switch to the HMI. It is common for only one type of proprietary Internal interface to be provided since the radio control panel is also proprietary. Although Internal Interfaces may be physically part of the Main Switch it is useful to regard them as separate components because they often contain special software or firmware that is independent of the main switch and control system.

2.4 External

Interfaces

External Interfaces connect the main switch to the radio transmitter and receiver equipment. External interfaces may be of several types to suit transmitters/receivers that are locally connected to those that require remote Radio Control Equipment (RCE). Many manufacturers also provide RCE as an integral part of the external interfaces since there are no common standards as compared with external telephone lines. Unless the RCE is also provided by the same VCS supplier problems with interfacing can be encountered. Due to the specialised nature of RCE these guidelines do not include any details of them

2.5

System Management / Engineering Terminal

A System Management / Engineering Terminal can provide a multitude of facilities ranging from the configuration of an HMI through to the collection of system performance parameters. It is common for such terminals to be PC-based systems with sophisticated software to provide a user-friendly interface in order to carry out either tedious or complex tasks. Where a VCS supports both Radio and Ground Telephone services (see Section 2.3 above) a common system management / engineering terminal is often provided. Even when the Radio and Ground Telephone functions are not components of the same VCS, a common system management / engineering terminal could offer benefit in terms of maintenance and support. (Further information on System Management / Engineering Terminals is given in Part 5: section 1.4).

2.6 System

Configuration

Having described the component parts of the Air Ground Radio VCS as five subsystems above, there is no reason why (with the possible exception of the System Management / Engineering Terminal), such a system may not be supplied as a single unit including all components; such systems are often purchased either for very small operational units or as standby/back-up systems for large operational units as further described in Part 5: section 1.12.

3.

COMBINED GROUND TELEPHONE AND AIR-GROUND RADIO VCS

As stated in Sections 1.6 and 2.6 above both the Ground Telephone and the Air-Ground Radio sub components of a VCS may be provided as single units. Equally it is possible for a VCS to be provided that combines all the functionality of both the Ground Telephone and Air Ground Radio components. To which extent this potential feature is used, will be governed by the User requirements and the Security aspects (see Part 5: Section 1.5.2). Most applications in Air Traffic Management will, in fact, require the combined VCS as illustrated in the Table 1 below and throughout the ATM industry the term VCS is usually interpreted as a combined system.

Table 1: VCS – Typical Configurations

Ground Telephone Small Combined Telephone and Radio VCS Medium Combined Telephone and Radio VCS Large Combined Telephone and Radio VCS Flight Briefing Unit (FBU)

ü

ü

ü

ü

ü

ü

ü

NOTE: There is no firm definition of what constitutes a large, medium or small VCS, but for guidance purposes the following values can be used.

- Large VCS >700 ports; - Medium VCS 350 - 700 ports - Small VCS <350 ports.

Air Navigation Service Providers (ANSPs) who have a broad range of requirements as illustrated above may wish to consider the possible benefits in maintenance and support of having a common range of products to meet them. This concept can be extended such that the physical appearance of “Controller Working Positions” may be identical throughout an operations room. An example of this is the operational concept of the Tactical and Planner controller suite where the Tactical controller has both radio and telephone facilities whilst the planner may have telephone facilities only. The role or ‘mission’ of each suite (which radio frequencies and telephone lines provided etc) is simply a question of assignment or configuration carried out from a common System Management / Engineering Terminal (see Part 4: HMI 1). The role of each suite can thus be changed for both operational and engineering purposes.

PART 3

PART 3 - USER FACILITIES

1. GROUND

TELEPHONE

This section of the Voice Communications System (VCS) specification guidelines outlines the operational functions to support ground-to-ground telephone applications.

1.1

Primary User Ground Telephone Facilities

This section describes the primary ground telephone facilities required by Air Traffic Controllers and other operational personnel in order to carry out their duties of Air Traffic Management. Performance criteria as demanded by such personnel are included without any reference to the engineering facilities needed to provide them.

1.2 Definitions

and

Assumptions

The term 'Bi-lateral Agreement' refers to the appropriate authorities within the 'A'-party and 'B'-party ANSPs.

Busy

Terminal busy

The condition that arises when an incoming call has reached the 'B'-party CWP but there is no resource available to present the call to the user (see

User definition). The Terminal busy condition should not arise on a DA call (Part 3: Section 1.3.1) or an IA call (Part 3: Section 1.3.2), but is possible for an IDA call (Part3: Section 1.3.3) in the event that the incoming call queue is full. An illustration of what is meant by Terminal Busy is given in ANNEX C "Reference Model example for the Management of Incoming Calls".

NOTE: The condition of "User busy" in the sense of the User being occupied with other calls in progress while the call queue is not full is not relevant to these guidelines and is considered to be a matter of local operational procedure.

Network busy

The condition that arises when all speech paths between one VCS and another are either currently in use or (exceptionally) configured as out-of-service via the System Management Terminal.

Throughout these guidelines, the term "congestion" is used synonymously with "network busy".

Call parties

The terms 'A'-party, 'B'-party and 'C'-party are used throughout these guidelines to identify the users involved in a telephone call, as follows:

'A'-party: the user who initiates a telephone call – the calling party; 'B'-party: the user who first receives the telephone call – the called party; 'C'-party: any other party involved in an established call.

Dynamic display

A device used for the visual presentation of operational information such as caller identities, call status and programmable touch-keys.

Facility

The term 'facility' is used to describe the function to be carried out and the term 'Feature' gives further details or the particular attributes of the Facility

Key

Throughout these guidelines, the term 'key' is used to refer to a single activation device such as a key, switch, button or an icon

Normal/Abnormal

The terms 'normal' and 'abnormal' refer to when the Performance criteria defined for each Facility are either met or infringed respectively

Port

A communication connection point to a VCS. Normally, a single simple analogue telephone extension will be associated with a single port although other interface types may require the association of more than one port to each interface.

Supervisory Tones

The various supervisory tones and announcements used (when applicable) by the VCSs are detailed in Part 3: Section 1.7.1.

User

An Air Traffic Controller or other operational person carrying out the duties of Air Traffic Management.

NOTE: This definition does not include personnel carrying out administration and maintenance functions.

1.3 Access

Methods

There are three types of Primary Telephone Facilities by which calls can be made – known as "Access Methods"; these are:

· Direct Access;

· Instantaneous Access; · Indirect Access.

NOTE: The audible tones referred to in the sub-sections below should be provided to the User. The intention is to give an indication of the status of the called terminal or the network. However, in order not to distract the User from the task, in which they are engaged, the audible tones may be replaced by suitable visual indications. The types of which both audible and visual indications can be derived when external circuits are used will be dependent upon the signalling system used on those circuits.

1.3.1 Direct Access Facility Description

(a) With this facility the operation of a single key by the 'A'-party is all that is required to initiate a call.

(b) The 'B'-party address is assigned and fixed semi-permanently in the 'A'-party VCS and is thus uniquely associated with each key and each key is labelled as such.

(c) Dial tone and out-going signalling tones are not given to the 'A'-party. (d) Ringing tone should be given (and / or visually indicated).

(e) Busy tone shall be given if appropriate.

(f) Terminal Out-of-service shall be given should the call fail for any reason other than Busy.

(g) The 'B'-party is alerted to the presence of the incoming call by audio and or visual means as determined by the 'B'-party VCS.

(h) The 'A'-party identity is indicated to the 'B'-party either by association with a key assigned and fixed semi-permanently in the 'B'-party VCS or by means of a dynamic display.

(i) The 'B'-party must accept the incoming call by means of a single action associated with a key or dynamic display.

(j) Due to either the exclusive, one-to-one, assignments of the keys between the 'A' and 'B' - parties or reserved capacity in the 'B'-party dynamic display, it is abnormal for the 'A'-party to encounter the 'B'-party busy; this is a fundamental attribute of the Direct Access Facility.

(k) Under normal conditions the 'B'-party can receive one or more Direct Access calls and by observing the identities of the respective 'A'-parties, together with defined operational procedure or (more likely) operational experience, the 'B'-party will deal with each call appropriately in the appropriate sequence. (l) At the end of a call either the 'A'-party or the 'B'-party may be required to

de-select/clear.

Performance Criteria

(a) Direct Access is designed to meet the requirements for Direct Controller-Controller Voice Communication (DCCVC) which stipulates that communication be established between radar controllers within 2 seconds in 99% of the time [3].

(b) The interval of 2 seconds is the delay between the 'A'-party initiating the call (Section 1.3.1 para (a)) and the 'B'-party receiving the call alert/indication (Section 1.3.1 para (g)).

1.3.2 Instantaneous Access Facility Description

(a) With this facility the operation of a single key by the 'A'-party is all that is required to initiate a call; some ANSPs prefer, however, that it is necessary for the 'A'-party to sustain the key operation for the duration of the call.

(b) The 'B'-party address is assigned and fixed semi-permanently in the 'A'-party VCS and is thus uniquely associated with each key and each key is labelled as such.

(c) Dial tone and out-going signalling tones are not given to the 'A'-party. (d) Ringing tone is not given to the 'A'-party.

(e) 'Terminal Out-of-Service' tone is given to the 'A'-party should the call fail for any reason including any busy conditions encountered.

(h) An audible alert is generated at the 'B'-party VCS in accordance with the following options:

· no audible alert

· an alert of fixed duration

· a continuous alert requiring a silencing action by the 'B'-party.

(i) The 'B'-party VCS automatically accepts the incoming call without any intervention required by the User; this occurs regardless of the 'B'-party being engaged on any other type of call. Thus 'B'-party busy is totally abnormal and should result in Terminal Out-of-Service tone being given to the 'A'-party. At this stage the speech channel from the 'A'-party to the 'B'-party is established. The 'B'-party ANSP may decide to have any speech from the 'A'-party handled in one (or more) of the following ways:

· connected in conference with other speech at the 'B'-party CWP; · directed to a loudspeaker;

· directed to one side of a split-working headset;

· any other arrangement appropriate to the local operational procedures. (j) The establishment of the call as detailed in para (a) above may also result in the

'A'-party having some Monitoring facilities of the 'B'-party's Controller Working Position including ground - ground and air-ground radio telephony. This enables the 'A'-party to exercise discretion before passing the message. Although such monitoring will require the prior establishment of a bi-lateral agreement if two ANSPs are involved, it is recommended throughout the ECAC region.

(k) The 'B'-party may respond to the 'A'-party by activation of a key associated with the incoming call. This action enables the return speech path if it occurs during the current call; otherwise, it is treated as a new Instantaneous Access call. (l) If the 'B'-party responds during the current call, this has the effect of preventing

the call from being cleared until both parties clear the call; without B-party response, the call is cleared when the 'A'-Party terminates the IA-call.

(m) Call clearing has no effect on other calls in progress at either the 'A'-party or the 'B'-party.

Performance Criteria

(a) Instantaneous Access is designed to meet the requirements of Instantaneous Controller-Controller Voice Communication (ICCVC) which stipulates that two-way direct communication be established between non-physically adjacent controllers within 1 second or less in 99% of the time [3].

(b) The interval of 1 second is the delay between the 'A'-party initiating the call (Section 1.3.2 para (a)) and the 'A'-party to 'B'-party speech path being established (Section 1.3.2 para (i)).

1.3.3 Indirect Access

The Indirect Access facility enables a 'A'-party to enter a complete 'B'-party address on a telephone dialling keypad (or equivalent device) in order to select a network and to cause a call attempt to be made to the supplied address. This is equivalent to normal dialled telephone operation.

In addition to dialling the 'B'-party address in full, the following PBX-type Facilities are also used to establish Indirect Access calls:

· Abbreviated Dialling:

entering a short code (up to four digits, a character string of unrestricted length or a specific labelled key) on a telephone dialling keypad (or equivalent device), shall cause a call attempt to be made from the 'A'-party to a predefined 'B'-party associated with the supplied code;

· Last Number Redial:

the operation of a key, shall cause a call attempt to be made from the 'A'-party to the 'B'-party to which the most recent previous call attempt (successful or unsuccessful) was made;

Ringing tone and busy tone are given to the 'A'-party as appropriate. A suitable mechanism (i.e., Terminal Out-of-service tone) shall be provided to inform the 'A'-party, should the call fail for any reason other than Busy.

It may be possible for calls from more than one 'A'-party to be presented to a 'B'-party simultaneously. In such cases, the selection of the next call to be answered by the 'B'-party is determined either directly by the 'B'-party or on the basis of an operational parameter such as longest waiting time or the Priority of the incoming call (see Part 3: section 1.4)

It is possible for either the 'B'-party or the 'A'-party to terminate an established Indirect Access call.

Although the means of indicating the order of arrival is implementation specific, it is common for some form of stacking arrangement to be used. Consideration needs to be given to the maximum size of queue that would be considered manageable. Typically, a queue would be 5 or 6 calls deep.

The extent to which the call origin (identity of the 'A'-party) can be displayed will be dependent upon the signalling system when external lines are involved but it is recommended that a global identity should indicate the generic source of the call if a specific identity is not available. Some examples are given in Table 2.

Table 2: Examples of generic identities

Identity indicated Origin

ATSN Another user on the ATS network but without the means to indicate the ATSN number.

PSTN A PSTN user without 'A'-party

identity. The basic attributes of the Call Queuing facility are as follows:

· all calls in the queue are in a calling (ringing) condition until answered;

· a manual process may be used for selecting the next call to be answered but this does not preclude some form of first-in-first-out automatic selection; · Additional indications should be used to identify Priority Calls (Part 3:

Section 1.4) that have arrived in the queue. Such indications might include a unique flag against the queue entry, a different display attribute (e.g. flashing characters or a unique colour) and a distinctive audible alert.

Although it will usually be IDA calls that are directed to the Call Queuing facility, in some exceptional circumstances (most commonly fault or call diversion conditions) DA calls may also be placed in a call queue. In these cases, it is recommended that some additional means of identifying the call as a DA call is given.

An illustration of the use of a call queue is given in ANNEX C "Reference Model for the Management of Incoming Calls".

1.4 Call

Priority

The priority facility is a means of attaching an indicator (or flag) to a telephone call to show that it is "urgent" as opposed to "routine". It is intended for use when it is necessary to make an urgent call concerning the safety of aircraft (i.e., an emergency situation) and to enable, if necessary, the interruption of less urgent calls in progress at the time. Thus calls can be made with or without priority so that there are two types as follows:

· Priority Calls · Routine Calls

The ultimate decision and responsibility as to whether a call is a Priority Call rests with the 'A'-party in accordance with local operational procedures. There are 3 ways in which a priority call can be made:

i) manually before the call is made:

before making the call, operation of a priority key will set the call to "Priority". This method is used when the call is already known to be urgent;

ii) during call set up:

this method would be used as a reaction to an urgent operational situation that has arisen, including a delay in answering at the far end or on receipt of busy tone;

iii) automatic setting of priority:

the calls from a particular CWP or set of keys is pre-programmed in the VCS to be "Priority". This method can be used for operational reasons when calls made from a particular CWP or key are always to be treated as urgent. It is recommended that the setting of the CWP or keys for automatic priority is an easily selectable option by means of the system management terminal.

Equally, the 'B'-party VCS should react to an incoming priority call in the following manner:

i) provide some means of indicating that a priority call has been received (e.g. special visual and/or audible indications);

The priority call interruption implementation should also be available for VCSs acting as transit VCSs.

1.4.1 Intrusion by a Priority Call

In the event that the 'A'-party has made a Priority Call but encounters the 'B'-party busy, Intrusion should take place automatically. Upon Intrusion all Parties are connected together in conference (see Part 3: Section1.6.4). Before the Intrusion occurs a warning tone (see Table 3 in Section 1.7.1) should be given.

It should be possible for any user to be protected against intrusion by other users. This protection should be selectable either individually on a user-by-user basis or as a single parameter for all users connected to a VCS.

1.5 Simultaneous

Calls

A Simultaneous Call (SC) occurs when two Users call each other at exactly (or very nearly exactly) the same time. Simultaneous calls may arise as a result of any type of call (IA, DA and IDA) but the outcome will vary depending upon the specific situation prevailing at the time.

Overriding Principles

In all cases of simultaneous calls the following overriding principles will apply: a) Indeterminate call states and/or VCS conditions shall not arise b) Users shall not receive false, ambiguous or misleading indications c) Notwithstanding the specific situations described below the guaranteed

outcome for both Users shall be a “User Busy” indication.

Specific Situations

There are two specific simultaneous call situations that should be considered. These are:

1. Both Users Connected to the same VCS

2. Each User Connected to a separate VCS of any type

Situation #1 – Both Users connected to the same VCS

In this situation, within the performance criteria stipulated for Direct Access and Instantaneous Access (Part 3: sections 1.3.1 and 1.3.2 respectively), a simultaneous

Situation #2 – Each User Connected to a Separate VCS.

In this situation, within the performance criteria stipulated for Direct Access and Instantaneous Access (Part 3: sections 1.3.1 and 1.3.2 respectively), a simultaneous call attempt should result in one of the following outcomes.

a) Busy tone presented to the Users.

b) An automatic re-dial by each VCS after an interval of random length not exceeding 3s. If this attempt is also unsuccessful, the re-dial sequence should be repeated. If, after the second attempt, the re-dial sequence is unsuccessful, Busy tone should be presented to the User and the re-dial sequence stopped.

NOTE: By bi-lateral agreement the outcome (a-b) for simultaneous call attempts has to be defined for each access method (IA, DA, IDA).

1.6

Supplementary User Telephone Facilities

Most VCSs will have a wide range of PBX-type facilities and it is not the purpose of these guidelines to describe all of these in detail. The following Facilities are recommended as those most useful for ATM applications some of which can be found in the ICAO Annex 10 Recommendations [7]. It should be noted that these services are considered to be provided locally in each VCS with no specific requirement that they should interoperate with other VCSs in the ATS network.

1.6.1 Common Appearance / Ring Group

The Common Appearance service allows a number of users to be logically grouped for the purpose of receiving calls. Calls to a Common Appearance Group are presented to all members simultaneously for anyone to answer. Users need to be aware, however, that certain types of connection to remote VCSs can cause complexities with implementation (usually associated with numbering and addressing in modern signalling systems) and specialist technical advice is recommended if this facility is required.

1.6.2 Call Transfer

The Call Transfer service enables a user involved in an active call to establish a new call between the other user in the active call and a third party.

1.6.4 Conference

The Conference service enables a user to interconnect a number of Controller working positions and/or external lines of varying types, allowing full speech facilities to all connected parties.

NOTE: An established conference is maintained until only two parties remain connected (at which point it reverts to being a normal basic call). The conference is not released when the originator clears.

Consideration should be given to the complexities of managing conferences of more that 5 parties in an ATM situation before the dimensions of the conference are specified. It is also recommended that costs for having this facility are sought from potential suppliers and that checks are made if there are any regulatory restrictions (see Part 5: Section 2).

1.6.5 Call Pick Up

The Call Pickup service enables a user to answer a call that is in the alerting phase (ringing) at another user's terminal.

1.6.6 Call diversion

The Call Diversion service enables a user to cause all incoming DA and IDA calls to that user to be routed to another user in the following circumstances:

· unconditionally;

· if a busy condition is detected at the 'B'-party;

· if the 'B'-party fails to answer an incoming call within a predetermined time (no reply).

1.6.7 Group Hunting

The Group Hunting service allows a number of users, as a configuration option, to be associated in a group (a Hunt Group) with a single address. Calls to that address will be routed to one of the users in the group using a predefined distribution algorithm.

NOTE: The difference between the Group Hunting service and the Common Appearance service is that a call to a Hunt Group causes only one member of the group to be alerted whereas a call to a Common Appearance group causes all members of the group to be alerted.

In addition to the Hunt Group address, each member of a Hunt Group may also be assigned a unique address from the VCS numbering plan.

1.6.8 Call Completion/ Call back On busy

The Call Completion Facility enables the completion of an Indirect Access call to another user, which was unsuccessful because a busy condition was encountered at the “B” party;

1.7 Additional

Service-Related

Guidelines

A VCS should be capable of providing call parties with audible tones, as recommended in Table 3 below, to indicate call progress.

Table 3: System tones

Tone Purpose Frequency

(Hz)

Period

Dial Returned to a user when that user indicates to the system readiness to dial (for example, taking the telephone set off-hook).

425 continuous

Ringing Returned to the 'A'-party after successful call establishment and prior to call acceptance.

425 (1 s on,

4 s off), repeated Terminal busy Returned to the 'A'-party if all

available voice paths to a user are occupied.

425 (0.5 s on,

0.5 s off), repeated Congestion

(Note 1)

Returned to the 'A'-party if a call cannot be completed to the required 'B'-party due to all appropriate inter-VCS links being occupied or otherwise unavailable.

425 (0.5 s on,

0.5 s off), repeated

Number Unobtainable (Note 2)

Returned to the 'A'-party if a terminal is "Out of Service" or the 'B'-party address is unassigned.

1000 (0.5 s on,

0.5 s off), repeated

Interrupt warning (Note 2)

Injected into the voice path to warn a party of the imminent priority interruption of an established call.

1000 (40ms, 0.5s off) repeated for up to 15s prior to forced disconnection Intrusion warning (Note 2)

Injected into the voice path to warn a party of the imminent priority conferencing of an established call

1000 1 s on

Note 1: The recommendation for congestion tone is the same as that for busy tone. If users wish to distinguish between the two tones, a dual frequency tone, e.g. 425Hz / 1000Hz (0.5s each; repeated) can be used.

The tones in Table 3 conform, wherever possible, to those specified in ITU-T Recommendation Q.35/E.180 [20]. Regional variations in the tones generated by a VCS are possible where:

· the tones are generated by the local VCS;

· the tones are transmitted to another VCS and a bi-lateral agreement exists between the two ANSPs involved.

2. AIR-GROUND

RADIO

This section describes the radio functionality recommended at a Controller Working Position (CWP) where Air-Ground Radio facilities are required. It does not specify how this functionality is to be achieved technically or the parameters within which the radio system shall operate.

Although not necessarily required at every CWP, all functions should be supported by the VCS, and be capable of being assigned to CWPs as required.

2.1 Definitions

and

Assumptions

A device used for the visual presentation of operational information such as radio frequencies selected, frequencies in-use / aircraft calling.

Key

Throughout these guidelines, the term 'key' is used to refer to a single activation device such as a key, switch, button or icon.

User

An Air Traffic Controller or other operational person carrying out the duties of Air Traffic Management.

Push-to-talk (PTT)

PTT is the User action of operating a key to transmit on one or more radio frequencies. The PTT key itself is invariably a mechanical device spring loaded to de-activate upon release but some operational applications require the use of a PTT lock-on mechanism.

Aircraft (A/C) Call

A/C call is a visual indication presented to the User that a particular frequency is active due to the reception of a carrier frequency by one or more receivers. A/C call is often associated with ‘Mute Lift’ or ‘Squelch’. How A/C call is conveyed to the CWP is beyond the scope of these guidelines.

Radio Frequency

The term Radio Frequency is used to refer to a nominal ATC – frequency such as 123 decimal 00 (25kHz spacing), 123 decimal 000 (8.33kHz spacing).

Radio Channel

The term ‘Radio Channel’ is used to specify the nominal centre frequency in conjunction with a specific radio location when in fact the actual frequency used may be an off-set of the nominal sector frequency. Furthermore a radio channel always defines at least a logical transmission line, very often it specifies the VCS’s physical radio interface.

Radio Coverage

The radio coverage is the airspace in which a frequency is usable. The use of more than one Tx/Rx equipment to control the extent of radio coverage is useful in some circumstances:

· Airspace size

· Geographical considerations (mountains, sea..) · Main and standby radio coverage

Remote/Radio Control Equipment (RCE)

In situations where transmitters (Tx) and receivers (Rx) are remote from the main VCS equipment some form of Remote Control Equipment (RCE) may be required. In essence RCE is designed to provide two-way remote control and telemetry using a variety of interconnections ranging from dc cables, Network operator provided analogue or digital links to public and private radio links. Thus the RCE ‘bridges the gap’ between the VCS and the Tx / Rx equipment.

Specification of RCE is beyond the scope of these guidelines, but it must be compatible with the VCS interfaces.

ANSPs may perceive the provision and management of RCE as an autonomous facility in which case problems can arise with specifying the interfaces and agreeing points of demarcation with several parties involved.

Although these guidelines provide no RCE specific details the following two sets of facilities and services are common

requirements:-Tx / Rx Services

Voice

Push-to-talk (PTT)

A/C call or Squelch

Automatic Gain Control / signal strength

Equipment status

Site Management Information

Door contacts

Fire alarm

Intruder alarm

Power failure

2.2.2 Modes of Operation

Radio access at a CWP is activated by the operation of a key associated with a particular frequency. The key enables a particular radio frequency to be in one of four modes:

·

Off/Deselected

·

Receive only (Rx)

·

Transmit and receive (Tx/Rx)

·

Cross-coupled

2.2.3 Receiving - frequency active

When ‘Rx’ mode has been selected the User can hear any transmissions that are made on that frequency. At the same time the presence of the carrier frequency, regardless of speech modulation, will also cause the A/C call visual indication at the CWP.

2.2.4 Audio Device Selection – Rx Mode

Information on audio devices is given in Part 4 (HMI), Section 1.2.

This facility enables the User to select whether transmissions received from aircraft are directed to either a headset or loudspeaker at the CWP.

For safety reasons, the system should have to ensure that:

a) Once the audio device selection for a specific radio channel at a CWP has been completed, this should be indicated to the user.

b) The selection of audio through a headset should only be allowed if the headset jacks are plugged in the CWP. Compliance with this requirement will enable the radio channels selected in the headset to be automatically deselected from the headset and selected in the loudspeaker when the jacks are removed. The loudspeaker volume should be adjustable by the User, but with a limited minimum according to operational requirements; some means of indicating that the loudspeaker volume is at minimum should be provided. These measures should guarantee that the audio can be heard at the CWP.

c) It is not possible to select a frequency without having an audio device (headset or loudspeaker) connected.

d) Any frequencies that have been enabled on the VCS do not go unmonitored by always ensuring that they are Rx selected on at least one (typically a supervisor’s) CWP.

Jack-coded plug-in devices (such as headsets) are commonly used to

determine which (if any) audio devices are connected.

2.2.5 Transmitting

When both receive and transmit (‘Tx/Rx’) mode has been selected the User can transmit on the frequency by operating a ‘Push-To-Talk’ (PTT) key. It should not be possible to transmit on a frequency without receive also being selected.

2.2.6 Side Tone

When transmitting, Side Tone is the User’s own speech fed, at reduced level, into the User’s ear-piece in Hand Microphone Telephones or Headsets. Side tone may be generated locally by the VCS or from speech received “off-air” via a receiver. The latter method has the advantage of proving, to some extent, that the system is working but complexities associated with audio delays, phase shifts and multiple receiver operation often precludes its use.

2.2.7 Multiple Frequencies

A CWP may have radio access to several frequencies, each of which can be set individually in one of the four modes described in section 2.2.2 above. Thus simultaneous reception on more than one frequency is possible; similarly simultaneous transmission on more than one frequency is possible by operation of a common PTT key. The total quantity of frequencies that can be accessed simultaneously at a CWP will be specified by the ANSP.

2.2.8 Transmitter / Receiver Selection

ANSPs may require that the extent of radio coverage for each frequency can be controlled by transmitter and/or receiver selection; several options are available.

· Option 1:

Individual transmitter and receiver selection is either a VCS or RCE configurable parameter. The User has no means of selection available at the CWP.

· Option 2:

The User can select at the CWP, which transmitter and receiver combinations are in use on each frequency. The quantity of transmitters and receivers and permissible combinations – including default settings -will be specified by the ANSP.

· Option 3

NOTE: The issue of co-frequency and other types of radio interference as well as audio phase interference and additional complexity in conjunction with cross-coupling are beyond the scope of these guidelines.

2.2.9 Main and Standby Radio Coverage

ANSPs may require standby radio coverage for each frequency. The means of

selection and control of such coverage will be specified by the ANSP but the following are typical switching possibilities:

· Automatic switching on line failure or transmit/receive loop failure detection · Switching on command of the System Management/Engineering Terminal · Manual switching directly on radio interfaces

2.2.10 Frequency Cross-Coupling

Cross-coupling may be applied to two or more frequencies but the principles may be illustrated with reference to two cross-coupled frequencies ‘A’ and ‘B’ as follows. If an aircraft transmits on frequency ‘A’ it is received on the ground and ‘cross-coupled’ to be re-transmitted on frequency ‘B’. For the User on the ground when they transmit on either frequency ‘A’ or ‘B’ both transmitters will be activated at the same time.

How cross-coupling is effected is beyond the scope of these guidelines and the extent (two or more frequencies) will be specified by the ANSP. Also the means of selection and control of cross-coupling will be specified by the ANSP but the following are typical options:

· At any CWP

· At a specified ‘supervisor’ CWP

· By means of the system management terminal

Whatever means of cross-coupling is selected it is extremely important that the User (or Users) are given clear indications which frequencies are in cross-coupled mode.

NOTE: Operational safety hazards, particularly during busy/heavy traffic situations, may arise due to cross-coupling where the chance of missed or disturbed radio transmissions increases significantly. These operational safety hazard considerations are beyond the scope of these guidelines.

In view of the safety hazards outlined above consideration should be given to restricting the extent of cross-coupling as

follows:-· limiting the number of frequencies that can be cross-coupled ·

· limiting the number of cross-coupling sessions for the whole VCS

It is also important, in order to prevent coupling chains, to ensure that a particular frequency can only be included in one coupling session.

2.2.11 Use of Optional Channels

This facility enables an authorised User to configure access, by pagination or any other means, to ‘optional channels that had not been pre-configured at the CWP.

2.2.12 Short-Term Recording

The CWP should provide a local short-term digital recording and instant replay function of the last radio communications (minimum 3 minutes duration).

PART 4

PART 4 - HUMAN-MACHINE INTERFACE (HMI)

1. GENERAL

Each User interfaces with the VCS through a Controller Working Position (CWP) which provides a means of communication for both Ground Telephone and Air-Ground applications. The Features and attributes of the HMI are perhaps the most critical part of the VCS design since they have a direct impact upon the efficiency and safe working of Users. Some guidance on HMI aspects are given in this section but it is recommended strongly that the best way of selecting HMI is to permit Users the opportunity to try them out, at length, in realistic situations.

As stated in Part 1 these guidelines can only offer some general information on the HMI for Air-Ground applications. For the Ground Telephone part there are also no strict rules regarding the physical design of the CWP but ANNEX C provides a typical model on its layout and functionality.

There are also strong preferences throughout Eurocontrol’s ANSPs as to the extent of separation that should be provided between the Ground Telephone and Air-Ground components of a VCS. Some ANSPs require that as much separation be provided as possible with perhaps only a headset being a common device. On the other hand some ANSPs prefer a totally integrated solution with Ground Telephone and Air-Ground sharing common systems including all aspects of the HMI. These guidelines make no recommendations on these matters but some points for consideration are given in PART 5: section 1.5 (Modularity).

1.1

Activation and presentation devices

A CWP uses a range of activation and presentation devices to provide access to all of the user-functions implemented by a VCS. These devices may include, but are not limited to:

·activation devices:

- touch-sensitive screens;

- mouse or tracker-ball pointers in conjunction with screen icons; - physical push-button switches;

- keyboard or keypad;

- for the Air-Ground Push-to-talk (PTT) operation (See Part 3: section 2.1) mechanical keys are preferred including those that are integrated into hand microphones, desk-mounted, floor/foot switches and free or clip-on lapel switches integrated into a Headset cable

·presentation devices: - CRT monitor; - plasma display; - LCD display; - LED or LCD indicators - illuminated keys.

The ability to re-configure the layout of a User's VCS panel is often a requirement that prescribes the use of dynamic displays for both activation and presentation. Displays with segmented touch-sensitive screens are popular devices for this purpose.

For the future there may also be a trend towards total integration of the CWP to include all services – radar, radio, telephone etc – for which computer graphic displays and on-screen selection via mouse-type input devices are likely solutions.

1.2 Audio

Devices

The audio devices that are common for use by European ANSPs include a combination of the following devices:

· Headsets including Telephone/Radio Split Headsets and noise-cancelling microphones

· Moveable Desk microphones · Fixed Boom Microphones · Hand microphones · Loudspeakers

· Hand Microphone Telephones (telephone handsets)

In addition to personal preferences, the choice of which devices to be used is greatly influenced by the CWP ergonomics and the working environment. Some of the

· Obscuring – cables and fixed devices obscure displays and panels etc · Noise nuisance arising from both the ambient environment, adjacent Users

and loudspeakers etc · Feed-back

Audio management and planning across the whole workplace (control room) is thus an important criteria to be considered as part of the VCS specification not only from the perspective of the local Users but also for remote Users including pilots on the flight deck.

1.3

Management of Mixed Air-Ground Radio and Ground Telephone

Communications

The use of the audio devices, described in the section 1.2 above, is subject to ANSP and local preferences, but one of the more complex situations to be considered is the Tactical Controller in an Area Control Centre who uses both Air-Ground Radio and Ground Telephone communication facilities. The principle problem in this type of situation is that a pilot can have no knowledge of how the controller he is about to contact may be engaged with Ground Telephone calls. A similar problem may also arise with other Air-Ground Radio calls but it is assumed that these are covered by established operational procedure.

It is generally (but not exclusively) agreed that Air-Ground Radio communications takes precedence over those of Ground Telephone i.e. the Radio is always heard. One way of accomplishing this is by the use of split-headset working.

Split-Headset Working

In this configuration, the controller for all outgoing speech uses a common headset microphone. Incoming Ground Telephone calls will always be routed to one ear-piece. While a Ground Telephone call is in progress, an incoming Air-Ground Radio call may trigger one of the following effects:

a) Ground telephone speech is suppressed and both ear-pieces receive the Air-Ground Radio call.

b) The Air-Ground Radio call is routed to one specific ear-piece.

When the controller replies by activation of his PTT key, the pilot receives the transmission in the usual way. Some ANSPs also allow the remote telephone caller to hear the controller’s response to the aircraft, others prefer that it is suppressed.

A Safety hazard may arise by mixing air-ground and ground-ground calls. Thus facilities combining A/G and G/G-voice should be carefully considered.

Ground telephone calls are never mixed, inadvertently with Air-Ground Radio transmissions to the pilot.

Other Variations

Other variations include the

following:-a) use of separate telephone and radio audio devices b) common loudspeaker and common microphone

c) Instantaneous Access (IA) calls always routed to a separate loudspeaker sometimes with a latching indicator so that the calling party may be identified.

1.4 Training

Facilities

A means of monitoring may be provided to enable a suitably authorised User to listen in on voice communication from one or more other User terminals.

1.4.2 Student / Mentor Facility

The Student/ Mentor Facility is similar to the Monitor Facility described in section 1.4.1 above, but is specifically associated with an individual Controller Working Position (CWP). It includes a monitor Facility, but the Mentor is also able to activate their own microphone whilst at the same time disabling that of the Student so that they can take executive control of the conversation. This facility is particularly important for Radio applications when Student's are undergoing on-the-job training, but is applicable to both Radio and Ground Telephone facilities.

1.5

Human engineering guidelines

The following guidelines identify some important human engineering aspects that should be considered for Human Machine Interfaces (HMI):

c) A HMI should immediately make it clear to the controller that invalid data has been entered.

d) Any message, instruction or information should be displayed for a sufficient period to allow the controller to read it.

e) Display attributes such as colours, bolding, flashing and highlighting should only be used in those situations where the impact they cause is essential. Over-use can be distracting and can lead to important messages being ignored.

f) The current status of all function keys and direct access keys should be obvious at all times.

g) Any change in the status of a function key or direct access key should be highlighted by an appropriate means.

h) The availability of a particular function or service should be shown by the status of the indicator associated with the key that activates the service.

i) The indicator associated with a Direct Access key or an Instantaneous Access key should use different attributes (for example, lit, unlit, coloured and flashing) to distinguish between:

· an active call in progress;

· no active call or service in progress (idle); · an unanswered incoming call;

· priority calls · busy/congestion.

j) The indicator associated with the A/C call should be distinctive to enable active frequencies to be easily identified.

k) A distinctive and clear indicator showing any frequencies that have been cross-coupled should be provided.

l) A set of keys grouped to represent a standard telephone dial-pad should be available for the entry of numeric (address) data.

m) It should be possible to configure the keys and indicators of touch sensor devices (TSD) for left-handed as well as right-handed operation.

n) Great care should be exercised in the choice of displays/indicators to be used so that they are usable in the actual physical HMI

· Viewing angle

· Adjustable Brightness (day, night, sun glance operation etc).

· Light reflections obscuring visibility · Adjustable tone volume

· Selectable tones

Particular consideration should be given to the sensitivity and feel of push-buttons as well as feedback on activated touch sensors.

1.6

Physical Environmental Considerations

The keys, panels and displays associated with a VCS are usually located in a combined Work Position that houses the HMI of many other systems comprising the CWP. Care should be taken to ensure that the various components can co-exist in the physical environment intended and that the environment itself is suitable.

Particular consideration should be given to addressing the following known problems: · Electrical interference from adjacent units;

· Inadequate ventilation and excessive heat generation, the latter of which may demand air conditioning for components that would otherwise not need it;

· Noise generation by cooling or storage devices should be avoided, thus no fan or mechanical disk drives should be used for VCS operator position equipment

· All touchable equipment (keys, switches, touch sensor devices etc.) should be of such kind that it doesn’t feel cold or hot

PART 5

PART 5 – ENGINEERING GUIDELINES

1. ENGINEERING GUIDELINES

This section of the Voice Communication System (VCS) Procurement Guidelines addresses some of the technical requirements to be met by a VCS. In keeping with the overall purpose of these guidelines (as outlined in the Introduction to this document in Part 1: Section 1) only those matters considered to be of particular relevance are covered and this is not a full and comprehensive technical specification.

Each of the parameters described in this Part will be classified as follows:-(General) - applicable to both Ground Telephone and Air Ground VCS (Telephone) - applicable to Ground Telephone VCS only

(Radio) - applicable to Air-Ground VCS

1.1

Availability, Reliability and Maintainability (ARM)

(General)

Mean Time Between Failures (MTBF)

The average interval of time that a component or system will operate before a service-affecting failure.

Mean Time To Restore (MTTR)

Average amount of time needed to repair/replace a component, recover a system, or otherwise restore service after a failure.

NOTE: For guidance purposes a value of 15 minutes to replace a board/module and 1 minute for system recovery would be a reasonable performance figure for a modern VCS.

Availability

The availability of any system is simply defined as follows:

MTBF ty

Availabili

+ =

The availability of a VCS should be in excess of 99.999%. Modern technology makes this a realistic target for commercially available PBXs and terminal equipment.

It should be noted, however, that the availability for Air-Ground services in terms of maintaining radio communications with aircraft is quoted as 99.99999%. This would not be realistically achievable with one VCS on its own. It can, however, be achieved by the use of autonomous standby or back-up VCS, transmission technology and radio equipment.

As a 99,999 % availability figure is viable and realistic with today’s commercially obtainable VCSs, it should be considered to what extent the availability of specific services contribute towards the “availability” of the overall VCS. For example guaranteed leased line availability is often defined at less than 98,5%.

To achieve the necessary availability figures, stand-by and back-up features are an essential part of system design and configuration.

1.1.2 Reliability

(General)

The reliability of a VCS can be expressed in terms of the Mean Time Between Failures (MTBF) of individual Printed Circuit Boards (PCBs) but an MTBF for the overall system is probably more useful. The MTBF value will depend on the exact configuration installed but, as a guide, an MTBF in excess of 5 years would be reasonable for the complete loss of all telephony, voice and data services in a non-redundant (single central processor) VCS.

1.1.2.1

Reliability and System Redundancy

The reliability of a VCS is influenced significantly by the use of system redundancy. At a fundamental level, for example, individual external interface cards may be deployed in parallel so that in the event of a fault occurring in one of them the second one will continue to provide the service without any fault apparent to the User. This philosophy can be extended to the provision of duplicate processing for central control systems or even dual processors for autonomous multi-control systems. When requesting MTTR and MTBF figures from VCS suppliers, however, it is strongly recommended that the bases of these are clearly defined and also whether they have been sourced on actual performance data from products in the Field or by the use of

1.1.3 Maintainability

(General)

The maintenance of a VCS will be greatly simplified if the system is capable of detecting and reporting any faults that occur in its component sub-systems (e.g., PCBs) and to indicate the impact on the system of any reported fault. Once identified, it should be possible to replace the faulty sub-system while the VCS continues to function. Maintainability should be viewed from both hardware and system software perspectives.

1.1.3.1 Hardware

Easy access to the following VCS components should be available: · all PCBs;

· equipment shelves;

· line and power connections; · test points;

· diagnostic displays and indicators.

When system hardware changes need to be made (modifications or up-grades) it is important to know how this would be achieved, the time to carry it out and the full nature of any effects that the process may have on the operation and performance of the VCS.