Specifications

Appendix B. Null-Modem Cable
A null-modem cable allows communication between two similar devices. It is
sometimes called a crossover cable, because the transmit and receive lines are
crossed so that the two devices can communicate. An RS-232 null modem
cable usually also crosses other handshaking lines.
An RS-232 null-modem cable can be purchased at a local computer store. The
pin-outs for this cable are provided below.
Carrier Detect
1 ⇔ 4
Data Terminal Ready
Transmit Data
2 ⇔ 3
Receive Data
Receive Data
3 ⇔ 2
Transmit Data
Data Terminal Ready
4 ⇔ 1, 6
Carrier Detect, Data Set Ready
Signal Ground
5 ⇔ 5
Signal Ground
Data Set Ready
6 ⇔ 4
Data Terminal Ready
Request to Send
7 ⇔ 8
Clear to Send
Clear to Send
8 ⇔ 7
Request to Send
Not Used 9 9 Not Used
B-1