Model 3921Plus Multiport Modem; Model 3921Plus Multiport Carrier-Mounted Modem - Paradyne COMSPHERE 3920PLUS Technical Reference Manual

Model 3921Plus Multiport Carrier-Mounted Modem

The Model 3921Plus multiport is a carrier-mounted modem (Figure 1-4) equipped with an integral
time division multiplexer (TDM) with a modem sharing device (MSD). The modem installs into
the COMSPHERE 3000 Series Carrier, occupying two slots. The modem's faceplate covers two
slots in the carrier. It has twenty (20) LED status indicators for displaying modem activity and an
audio speaker jack for the carrier's optional speaker.
The modem's back panel has four edge card connectors that mount into two connector plates. Each
connector plate has two DB-25-S connectors providing four EIA-232-DTE interfaces.
Both the singleport and multiport Model 3921Plus modems derive ac power from the
COMSPHERE 3000 Series Carrier's backplane, which is a common bus to all devices installed in
the carrier. The user interface to any Model 3921Plus modem is through the shared diagnostic
control panel (SDCP), an optional feature which operates in a manner similar to the DCP on the
Model 3920Plus modems. For a better understanding of DCP operation, refer to Chapter 3,
DCP
Status
Pwr
Alrm
142 Test
Dial
125 RI
Busy
Serv
SQ
1 3
Port
2 4
103 TXD
104 RXD
105 RTS
106 CTS
107 DSR
108 DTR
109 LSD
Front Panel
Spkr
3921Plus
3920-A2-GH30-40
Operation.
FACEPLATE
Figure 1-4. Model 3921Plus Multiport Modem
October 1998
EDGE CARD
CONNECTORS
BACK
CONNECTOR
PLATES
PORT
1
PORT
3
PORT
2
PORT
4
Introduction
49614423a-03
1-5