Installation manual

4
February 2002 3920-A2-GK41-60
Model 3921Plus Singleport Carrier-Mounted Modem
The Model 3921Plus singleport is a carrier-mounted modem (Figure 2) capable of either 4-wire/2-wire
leased-line or dial operation. The modem installs into a COMSPHERE 3000 Series Carrier, occupying a single
slot. The modem’s faceplate has sixteen (16) LED status indicators for displaying modem activity and an audio
speaker jack for the carrier’s optional speaker.
The modem’s back panel has two edge card connectors that mount into a connector plate. This connector plate has
two DB-25-S connectors, one providing an EIA-232-D DTE interface and one for future functionality.
FACEPLATE
496-14178a-04
EIA232/V.24
EDGE CARD
CONNECTOR
FUTURE
USE
BACK
CONNECTOR
PLATE
V.35
(3600/3500)
RS366A/V.25
(3800)
EIA232/V.24
TXD
RXD
RTS
CTS
DSR
DTR
LSD
103
104
105
106
107
108
109
Pwr
Alrm
Test
Dial
RI
Busy
Serv
SQ
Status
Front Panel
3921 Plus
142
125
Spkr
EIA232/V.24
CONNECTOR
FUTURE
USE
GROUNDING
TAB
Figure 2. Model 3921Plus Singleport Modem