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MODEM Requirements
Although there are default settings for three MODEMs, other MODEMs can be
cofigured to operate with DVST.
As the settings vary from manufacturer to manufacturer there is not a set series of
commands that are guaranteed to work. The following tables detail possible
configurations, all should be checked against the MODEM manual. Before attempting
these suggested settings the MODEM should be reset to factory defaults with the
command AT&F or ATZ
The following settings are required as a minimum:
All modems:
Action required of MODEM Possible AT settings
DCD (Data Carrier Detect, sometimes abbreviated to
CD) must be set to follow the carrier. This signal
indicates to the DVST that a connection to another unit
has taken place.
&C1
The call must disconnect on a high to low transition of
DTR (Data Terminal Ready).
Only answer a call if DTR is present.
&D2
Auto-answer may be set if required. S0=1
Check MODEM manual
Country specific
Echo commands. E1
Synchronous Modems:
Extra action required of Synchronous MODEM Possible AT settings
Asynchronous mode must be set to dial the number
and the modem must switch to synchronous mode on
carrier detect.
&M1
Flow control must be disabled. &K0
Check MODEM manual
The modem should ignore RTS. &R1
Asynchronous Modems:
Extra action required of Asynchronous MODEM Possible AT settings
Asynchronous mode must be enabled. &M0
Flow control must be enabled on RTS/CTS. &K3
Error correction enabled ( if needed ). Refer to MODEM manual
Note It is strongly recommended that once the modem has been configured as above, it is set
in such a mode that this configuration is recalled automatically on power up. This will
help to ensure correct operation after a power failure. Consult you modem instructions
for details of how to achieve this.
Page 24 Dedicated Micros Ltd
Modems DVST Installation Guide