Connecting Modems; Altpin - Digi PortServer/8 User Manual

Connecting Modems

Modems are generally equipped with DB-25 connectors, so it is usually necessary to buy or build
an adapter such as the ones mentioned previously. Since the modem control lines, RI (Ring
Indicator) and DCD (Data Carrier Detect) are on pins 1 and 10, respectively, of Digi's RJ-45
jack, the adapter cable provided by Digi is ideal, since it has a 10-pin RJ-45 plug, and is
terminated in a modem-ready, DTE-configured DB-25 plug.

Altpin

If you want to use 8-pin RJ-45 to DB-25 adapters, a software feature called ALTPIN has been
incorporated into the PortServer software to swap the DCD and DSR signals. This makes DCD
available on pin 1 of an 8-pin RJ-45 connector.
RJ-45 ALTPIN WIRING: 8 PIN PLUG TO 10 PIN JACK
Digi device drivers do not require DSR in modem-control applications, and since almost all of
today s modems have auto-answering capability, the Ring Indicator signal is generally
unnecessary.
Note that to use Altpin, you must also configure the PortServer port for Altpin; see set flow
on page 45.
altpin
PortServer Terminal Server Ÿ Page 97