3Com AccessBuilder 980/000048/001 User Manual
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Contents
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3-2 CHAPTER 3: TROUBLESHOOTINGModem - DTE ConnectionModem does not accept or echo back AT commandsCheck that the cable between the serial port of the DTE and the modemis a standard RS232 cable. If the cable is bad, replace it. (Null modemcables, also known as cross-over cables, do not work in this application).A limited number of dumb terminals require DCD before they can talkto the modem. If this is the case you have to use a breakout box toraise DCD to the terminal. You can then configure the modems to forceDCD using the AT&C0 command.Check that the character echo command is enabled using the ATEcommand.Check that the DTE dialler type configuration option is set to AT. Referto the AT&M or AT&Q command description.Check that the response codes configuration option is enabled usingthe ATQ command.Make sure that all AT commands are terminated with a carriage return.Check that the ASCII value of a carriage return matches what is used bythe DTE and the modem (defined using S-Register S3).Check that the DTE and modem are using a compatible character format.Valid formats include 8 data bits with no parity, or 7 data bits with even,odd, mark or space parity.Check that the DTE’s data rate is supported by the modem. |
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