Four-Wire Direct Concentrator Wiring

Host Adapter or
Concentrator "Remote"
Port (HD-15 Male)
 
Concentrator
"Host Adapter" Port
(HD-15 Female)
Signal
Pin
Pin
Signal
RxD-
1
Connected to
1
TxD-
RxD+
2
Connected to
2
TxD+
TxD-
6
Connected to
6
RxD-
TxD+
7
Connected to
7
RxD+
GND
12
Connected (via shield) to
12
GND

In the Four-Wire Direct (EIA-422) wiring mode, the clock signals are encoded with the receive and transmit data signals, so only two twisted pairs are required.

The Four-Wire Direct cable is a twisted pair cable with a male HD-15 (high-density DB-15) connector at one end and a female HD-15 at the other end. The cable should be shielded, and the shield must be connected to the HD-15 connector shell at both ends.