I am trying to connect to an old varitrac (don't know if its a I or II). I have found lots of post of baude rates and flow control and the like. When we ordered the connectors for the varitrac board (it's a 25 pin on the board) to the 9 pin serial port on the computer Trane said the cable was no longer available. Does anyone know what the pinout or what type of cable is needed so I can make one?

Is it a null modem cable?

In the lower left corner of the board by the 25 pin connector there is a lable with the number 50100691 Rev 2 if that's of any use.