Hi, I have a device which sends data to a controller - but i want to replace the controller with something of my own. The problem; The 'device' does not send out any data (test with scope) unless the controller is hooked up. A scope on the controller confirms it is sending out packets. A scope on the device confirms it does nothing without controller. (device is definantly responding though, there is data being transfered when in normal operating conditions) There is only 2 wires. (i am told by manufacturer its RS422) So can RS422 send AND receive via only 2 wires ? (obviously not full-duplex). If so, then how can i 'fake' the controller. I have recorded from the controller what i need to say to the 'device' in order to make it respond, but my simple rs422/rs485 serial converter seems inadequate to the job. It implements a 4-wire system, 2tx, 2rx. So by tieing Rx1 to Tx1 and Rx2 to Tx2, i can send - but then i cant receive the response (through this converter).. Basically i need a way to receive this response, directly after sending a command to the device.. Any simple thing i can knockup from bits lying around - or is this something that i should really purchase. In which case, what should i buy exactly ? Thanks for any help!, Alex.