Talked to Zetron this week and here is the factory version of correct cable, I noted on the 48B manual in file section had a hand written Null cable written in, this will only work on receiving data and not talking to zetron controller.
PC RS232 2 3 3 4 5 5 ON PC SIDE cable JUMPER PIN 4 TO 6 AND PIN 7 TO 8 The color code for cable seems to change, so can not give you any help. I just cut the end off and used shrink tubing to seal the wires.Works well. Alex kr6g