The technical aspects of V90 or V92 on two analogue telephone lines (both side PSTN) or a so called a point to point connections.

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The technical aspects of V90 or V92 on two analogue telephone lines (both side PSTN) or a so called a point to point connections.

Even if this is a leased line connection or dial up connection the maximum line speed is V34 with 33600 bps never V90 or V92 56kbps. The reason is very simple for the protocol V90 (only a down stream from a maximum speed of 56K max. the upstream will only be 33600bps max.) or V92 (which also will allow you to reverse the 56kbps max. downstream to a 56000 bps max upstream) you need one side with a Central Side Modem (CSM).

So what is a Central Side Modem? This is a digital modem most common used by ISP (providers) on an ISDN line. This is not possible on an analogue line.

The theory of operating from V90:

There are certain special requirements and restrictions associated with V90 modems. In order for a users to obtain up to 56k upload speeds from their ISP, the telephone line had to be completely digital between the ISP and the telephone company central office (CO) of the user. From there the signal could be converted from digital to analog but only at this point. If there was a second conversion anywhere along the line 56k speeds were impossible. Also, the line quality of the user's telephone line could affect the speed of the 56k connection with line noise causing slow downs, sometimes to the point of only being marginally faster the 33.6Kbps connection. An important restriction with V90 is that while V90 modems can obtain up to 56Kbps download speeds, they are limited to 33.6Kbps upload speeds.

The theory of operating from V92.

V92 is the standard that followed V90. While it provides no speed increase when downloading from the Internet (56kbps appears to be the maximum speed for analog based modems), it does allow upload speeds to match the download speed provided both the ISP and the caller both have fully V92 compatible modems. It also adds two features. The first is the ability for users who have call waiting to put their dial-up Internet connection on hold for extended periods of time while they answer a call. The second feature is the ability to "quick connect" to one's ISP. This is achieved by remembering key information about the telephone line one is using to connect with and then using this saved information to help speed up future calls made from the line to the ISP. ISPs have been slow to adopt V92 due to the high cost of upgrading their equipment and the lack of demand by their customers to do so. With the rise in broadband take-up that has led to declining numbers of dial-up users, some ISPs have decided not to bother ever upgrading to V92.

The conclusion will be the maximum speed from a point to point connection through two analogue lines is always 33600 bps max.

Why limit a point to point connection through two analogue lines on 33600 bps max.? The reason is simple, this very complicated modulation methods will need a longer handshake (also called negotiating) time as a normal V34 connection. If both modems are V90 or V92 modems they will try the highest speed and have to go down to 33600 bps. In most cases this will take too much time. This will result in a disconnect because the carrier detect time on each modem is limited to a several time. This will result in tree times or more and in most cases no connection.

How to limit a modem in line speed?

You may use the correct AT command for early V90 modems with a dual chip solution this will be AT+MS=11 Later V90 and V92 single chip solutions AT+ MS=V34

First step go to the control panel by start > settings control panel.

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All screen grabs are based on Windows XP Pro. Windows 2000 or Windows 2003 (server) are more or less the same. Which steps to follow?

Go to the control panel by start > settings control panel.

Click on the modem and choose properties>

Choose Advanced and type the correct initialization, click on OK>

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Choose Phone and Modem options>

Click on the modem and choose properties>

Choose Advanced and type the correct initialization, click on OK>

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For older V90 modems not supporting AT commands phase 2 you may use the command below Go to the control panel by start > settings control panel.

Choose Advanced and type the correct initialization, click on OK>

Now you are ready for use with most dial up clients, who are not using the standard init from the .INF file. But be careful this is not always a solution because some applications known applications PC-Anywhere a Laplink Gold will send the initialization string each time they get a dial command or each time the connection from the called modem has been disconnected. The main problem with these applications is the initstring will be the one from the installed driver. So if the 56K V90 or V92 driver has been installed the application will put the modem back on V90 or V92 each time there is an out or incoming call.

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The answer is very easy install manual a standard V34 modem instead of the V90 or V92 driver. The screens below including instructions are for XP based PC’s, the layout from Windows 2000 or 2003 server may look more or less the same. The first installation will show you an external V90 RS232 (serial) modem, the second a V92 PCI modem, and the third a V92 USB modem.

Manual Modem installation for serial modems:

Make sure you do not connect or power up a serial modem before installing the driver

manually. Since Windows will activate the Plug and Play on the comport and will search for a matching V90 or V92 driver with a matching Plug and Play ID which is in the driver.

First step go to the control panel by start > settings control panel.

If there is driver installed you may remove this (wrong) driver. After removing this driver you choose Add and click on OK

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Use Standard Modem Types and choose Standard 33600 bps modem. Click on Next> You will see the screen below.

Click on finish>

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Manual Modem installation for PCI modems:

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You will see the screen below

Make sure you thick the radio button don’t detect my modem, I will select it from a list! Click on Next> You will see the screen below

Click on Next> You will see the screen below.

Now choose the com port which is connected to the modem. Click on Next> You will see the screen below.

Click on finish>

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This modem will give you a faster connection since the negotiating will start at V34 33600 bps max. Now make sure you choose this modem (and make it active) in you application like Laplink Gold

Manual Modem installation for USB modems:

Since the standard modems from Microsoft only are installable on COM1 or COM2 you need to disable COM2 on your motherboard if present to make sure your modem will be installed on COM2. Next step make sure you have installed the USB modem with the driver supplied with the modem on COM2 See below an example with the Tornado 563 V92 USB modem.

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Choose Add>

You will see the screen below

Click on Next> You will see the screen below

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Click on finish>

Now your modem is ready for use.

This modem will give you a faster connection since the negotiating will start at V34 33600 bps max. Now make sure you choose this modem (and make it active) in you application like Laplink Gold