Help please with TX and RX

[Rosscdo]

Hello,

New to this page and electronics.

I'm trying to work out what are my Tx and Rx are on a electronic piece of equipment so I can run a RJ45 jack to it.
Yes it sounds simple however to cable I'm using is army issue ethernet Bowman ETH one end and a 22 circular pin the other.i know only the first 4 pins are used, however it has no distinguishing features. So I must work from the BNAU (Bowman Network Access Unit) port. But I don't know how to test the pins to see what 2 pins Tx and what 2 Rx.

All help is appreciated.