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When troubleshooting modem connectivity problems and RAS errors related to hardware & modem connectivity problems (errors:

692
Hardware failure in port or attached device.

721
Remote PPP peer is not responding.

734
The PPP link control protocol terminated.) make sure you investigate these items:

1) Driver issue: Verify that you are using the correct and updated modem driver. Or run the add modem wizard and force it to select a “Standard X bps” driver to match the speed of the modem. The modem driver provided by the manufacturer is usually an INF file that adds various setup strings and response codes from the Hayes command set (AT commands) to the registry, and selecting the wrong driver can have negative effects. The Standard modem driver uses a very basic command set.

2) Modem speed: There are 2 different data rates involved with every successful modem connection:

1. Port Speed refers to the speed of the serial COM channel used by the computer to exchange data with modem. Port Speed can be set to a specific rate or to Auto via the Phone and Modems Control Panel. Lowering Port Speed slows the rate that the modem’s internal buffers fill, giving the device more time to push data onto the line, thus reducing packet loss. Lowering this value can sometimes rescue a bad connection by reducing the impact of line speed fluctuations on the quality of the received data.

2. Line, or Connection Speed, refers to the negotiated bandwidth of the modem-to-modem connection across the Telco line. It represents the maximum speed the 2 modems can exchange data in a given direction. Line speed and compression are negotiated by the modems during the connection process (all that whistling and screeching you hear if the speaker is on). Line speed and compression values are dependent on the quality of the entire Telco path at the time a connection is initiated. Both can vary widely during a connection and can be different in each direction. Line speed and compression are displayed in the dialup Connection Status window. These are static values and will not change even though the typical modem can dynamically compensate for line changes. Line speed and compression amount can only be set to specific values using Hayes commands.

Check the connection rate of your modem and try lowering the speed if you are having problems. Modems always connect at a lower bit-per-second (bps) rate than specified. The remote access server may not respond if your modem cannot operate at a higher bps rate. The inability to operate at a higher rate could also be because of the switching equipment between the client and the server or increased static on the phone line.

3) Modem settings: Check the other modem settings (hardware compression vs software compression, data & parity bits, etc)

4) App conflict: Make sure another application isn’t already trying to use the modem (Fax software, PC Anywhere, etc)

5) Different port: Trying plugging the modem into another serial port (Com 3 vs Com 2, etc)

6) New cable: Try another modem cable if available

7) New modem: Try another modem on the client if available (or server if the problem is that nobody can dial the server)
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