EIA-422 Eight-Wire Synchronous Modem Wiring

Host Adapter to Modem

C/X or EPC/X
Host Adapter
(HD-15 Male)
 
EIA-422
Synchronous Modem
(DB-37 Male)
Signal
Pin
Pin
Signal
RxD-
1
Connected to
6
RD-
RxD+
2
Connected to
24
RD+
RxC-
4
Connected to
8
RT-
RxC+
5
Connected to
26
RT+
TxD-
6
Connected to
4
SD-
TxD+
7
Connected to
22
SD+
TxC-
9
Connected to
5
ST-
TxC+
10
Connected to
23
ST+
GND
12
Connected (via shield) to
19
GND

Modem to Concentrator

EIA-422
Synchronous Modem
(DB-37 Male)
 
Concentrator
"Host Adapter" Port
(HD-15 Female)
Signal
Pin
Pin
Signal
RD-
6
Connected to
6
RxD-
RD+
24
Connected to
7
RxD+
RT-
8
Connected to
9
RxC-
RT+
26
Connected to
10
RxC+
SD-
4
Connected to
1
TxD-
SD+
22
Connected to
2
TxD+
ST-
5
Connected to
4
TxC-
ST+
23
Connected to
5
TxC+
GND
19
Connected (via shield) to
12
GND

The EIA-422 Synchronous Modem cables are twisted pair cables, each having an HD-15 (high-density DB-15) connector at one end and a DB-37 connector at the other end. The cable should be shielded, and the shield must be connected as shown in the diagram.