The Communication Link
Because there is more to the connection than the modem, all of the components
should be verified. A communication link consists of two computers, two
modems, and a dial-up telephone circuit. The installation may include a
dedicated leased-line rather than a switched central-office connection,
or a mainframe host with an asynchronous or synchronous front-end processor
at one end or the other. The general principles, however, are the same.
Your modem may be an internal one, that is, installed inside the computer,
the operational concepts are still the same.
The suggestions provided in the user documentation accompanying each Hayes
modem solve most problems in an installation. Most difficulties arise from
simple causes p; improper or loose connections or software incompatibility.
Review the scenarios and tips before assuming the problem is something more.
The suggestions in this section require familiarity with the Hayes Standard
AT Command Set, DTE requirements, RS-232/ITU-T V.24 signals, and the telephone
system.
A communication link problem may be due to a bad switchboard connection.
Before calling the local telephone system, however, you should ensure the
problem is not being caused by faulty or improperly connected equipment
at either end. Telephone service can be very expensive, especially if the
problem is not really with the phone lines.
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