HP 24SII - Manual (Page 51)

If you are connecting a device other than another BayTech product,
you must refer to the operator's manual for your equipment to
determine which pins are defined as TX+, TX-, RX+, and RX-.
If you are using 4-wire Operation and bidirectional Printer Sharing
Mode and connecting to another BayTech product (such as Tran-x),
please refer to
Appendix A.7.4 for the recommended cable pinout.
COMPUTER PORTS
NOTE: Computer ports using this configuration will support hardware
handshaking only. You must ensure hardware handshaking is
supported by the equipment that will connect to these ports.
Computer ports on the M24SII-V07 module using EIA-422 Protocol, 4-
wire Operation, and unidirectional Printer Sharing Mode utilize the
following pins and signals for communication:
RJ-11 PIN-OUT INFORMATION
PIN SIGNAL
EIA-422 DIRECTION DESCRIPTION
1 HSO+ Output Handshake Out (+)
2 HSO- Output Handshake Out (-)
3 RX- Input Receive Data (-)
4 RX+ Input Receive Data (+)