EXERCISES

5.1 DESCRIPTION OF THE OPERATING MODES

The operating modes have been described exhaustively in the previous chapter where the operation of keyboard and display is explained in detail.

This charter will explain some examples of use of the trainer.

5.2 EXERCISE 1: INSTALLING AND PREPARIG THE TRAINER

Open the upper protection cover.

Operator Panel:

• Screw the two whip antennas of the equipment onto the sockets ANTENNA IN and ANTENNA OUT

• Turn all the available potentiometers in clockwise direction • Select SW1 = SW2 = ON: select the channel CH

• Select SW5 = OFF • Select SW4 = TONE

• Check that no fault has been inserted: open the FAULT SIMULATOR and set all its microswitches Sn to OFF.

Follow the correct procedure for switching the Trainer on:

5. DO NOT ENERGIZE THE POWER SUPPLY (EXTERNAL

UNIT) via the power cord before completing the installation

correctly;

6. insert the plug of the power supply (external unit) into the rear socket available on the left side of the Trainer (seen from the back);

7. insert the female plug of the power cord into the socket of the power supply (external unit)

8. insert the male plug of the power cord into the mains socket of the laboratory.

When the Trainer must be RESET, remove the plug from the mains socket and then insert it again.

5.3 EXERCISE 2: ENABLING the 1st CONNECTION (USERS MS1 and MS2)

The display shows 1 to indicate MS1: press the PROGRESSIVE key

several times to set the trainer in this condition. Press 2 on the keyboard so that MS1 calls MS2.

The RING indicator of the user 2 starts blinking to indicate the handling-in of the call and the buzzer will ring with the same rhythm.

Pressing the button ANSWER of the user 2 will accept and enable the call.

The CONNECT LEDs of the users 1 and 2 are on to indicate the enabling of the call.

Observe the indication of the connection phases on the display.

The user 1 sends the tone of 2 kHz that can be adjusted with its own level control, to the user 2.

The user 2 sends the tone of 1.6 kHz that can be adjusted with its own level control, to the user 1.

5.3.1 ANALYZING THE SIGNALS

Use an oscilloscope.

The transmission clock TC (TP14) is the frame sync master clock (5 V, 64 kHz).

Fig. 5.1: TP14

The reception clock RC (TP15) is reconstructed in reception and is shown in the Fig. 5.2 (togethre with the TC).

Fig.5.2: TP14 – TP15

Check the signal sent by MS1 (2 kHz, max 1.5 Vpp) on TP12, and the same signal received by MS2 (2 kHz, max 1.5 Vpp) on TP11.

Check the signal sent by MS2 (1.6 kHz, max 1.5 Vpp) on TP10, and the same signal received by MS1 (1.6 kHz, max 1.5 Vpp) on TP13.

Observe the modulating signal MOD (TP25, 2 Vpp, period of 125 µS)

that uses a channel coding HDB3.

Use the signal available in TP16 (5 V, 8 kHz) that is the frame sync TS0, as sync signal.

Observe the demodulated signal DEMOD (TP26, 0.5 Vpp) that uses the

channel coding HDB3.

The fig. 5.4 shows DEMOD and TP16 (sync signal of the transmission

TSt0).

Fig. 5.4: TP16 – TP26

Change the frequency of the transmission or reception channel and observe the loss of the received signal: a FDM is simulated.

Observe how the received signals change as the parameters of the RF channel: NOISE and ATTENUATOR, are modified.

The signals sent by the users 1 and 2 are encoded by their respective CODECs.

In detail:

• the user 1 sends the voice information to the TS2 and it uses TSt2 (TP18) as sync signal

• the user 2 sends the voice information to the TS1 and it uses TSt1 (TP17) as sync signal

The fig. 5.5 shows the delay between TSt1 (TP17) and TSt0 (TP16). An analogous phase shift occurs for the other TSt and TSr.

The RX-MPX signal (TP27) that includes the complete reception frame

is shown in the fig. 5.6: TSt0 (TP16) is used as sync signal.

This is the visible signal in case of connection between the users 1 and 2.

Fig. 5.5: TP16 – TP17

Fig. 5.6: TP16 – TP27

5.4 EXERCISE 3: DISABLING the 1st CONNECTION (USERS MS1 and MS2)

Press the key DISCONNECTED of the keyboard, in the mode of user

1 or 2 (1 or 2 indicated on the display), to disable the connection in progress between the users1 and 2.

5.5 EXERCISE 4: ENABLING the 2nd CONNECTION (USERS MS3 and MS4)

Enable a further connection.

Press the PROGRESSIVE key several times to set the condition of

user 3: the same number will appear on the display. Press 4 on the keyboard so that MS3 calls MS4.

The RING indicator of the user 4 starts blinking to indicate the handling-in of the call and the buzzer will ring with the same rhythm. Pressing the button ANSWER of the user 4 will accept and enable the call.

The CONNECT LEDs of the users 3 and 4 are on to indicate the enabling of the call.

Observe the indication of the connection phases on the display.

The user 3 sends the tone of 1 kHz that can be adjusted with its own level control, to the user 4.

The user 4 sends the tone of 0.5 kHz that can be adjusted with its own level control, to the user 3.

5.5.1 MICROPHONE SIGNAL and TEST TONE

These signals can be supplied only to the user 4. It is necessary:

• to insert the jack connector of the microphone into the socket