14
6619-2202
PSTN
Network
Application examples
…
TDW-33 connected to TDW-33 with DTR signal call
DTR
DSR
DCD
Relay
External
application
10 kohm
May be required in harsh environments.
Configure the units
AT&F
Set the unit to factory default
AT&W
Store default settings
Set up the connection – The dialling modem
AT&Z0=nnn
Store the number of the remote modem in the dialling TDW-33
AT&S0
Set DSR signal always high (if this signal is used to trig the DTR)
AT&B1
Activates automatic DTR dialling if DTR switches from low (OFF) to high
(ON)
AT&W
Save settings
Switch DTR from
OFF to ON
The modem will now dial the phone number stored in the first location of
the telephone number table (AT&Z0=<nnn>)
Set up the connection – The answering modem
ATA
Enter the answer command when RING comes from the network or set up
ATS0=1 to auto answer on 1 RING signal (or more than 1)
NOTE:
If no valid DTR signal can be provided by external application, the modems
DSR signal can be used to trig the transmission. Connect the DSR signal via
a relay, or other potential free contact, to the DTR signal. A 10 kohm pull
down resistor should also be connected between the DTR and a signal that
is always low e.g. the DCD.
