Specifications

If you experience difficulty in establishing a communications path between your PC, modems,
and the digital telephone system, note the suggestions that are listed below.
•
Confirm that the modems are wired correctly. Be sure RD, TD, and SG are connected to the
system’s serial data connection. Reverse connections at pins 2 and 3 if necessary.
Sometimes you must strap pin 4 to 5, or pin 6 to 7, or pin 6 to 8 to 20 in the modem wiring.
Check the modem’s installation manual for this requirement. Also check the manual for any
additional wiring connections.
•
Use a breakout box data tester to troubleshoot the data communications lines.
•
Be sure that your modem has: auto-answer capability, DTR override, and CD override and
that the Result Codes, On-Line Echo, Off-Line Echo, and Flow Control are disabled. Plus,
make sure that you have enabled the modem’s auto-answer feature. The way to do this is to
program an initialization string into the modem. A typical initialization string that uses
generic modem AT Commands for connection to a telephone system’s serial data port is as
follows:
AT E0 F1 L2 Q1 S0=0 &C0 &D0 &K0 &W0 &Y0. Remember, this is a typical
initialization string—not all modems will respond to it. You should refer to your modem’s
instruction manual if you have difficulty.
Typical
Personal Computer
Data Jack
Line
Switch
Telco Network
Network
Jack
Data
Jack
Typical Common
Equipment Cabinet
Data
Port
Line
Port
Network Jack
Data
Modem
Data
Modem
dsu260.cdr
Installing A Personal Computer For Remote Programming
DSU II Digital Telephone System IMI66–132
Installing The DSU II Digital Telephone System 2 – 39