chrispol,
True the TW-523 is a 2 way device but what type of remote module are you trying to communicate with? As I stated before there are only about 2 or 3 different remote modules and 1 or 2 consoles that have 2 way communications capability. The TW523 may be trying to communicate with a remote but the remote does not have 2 way communications capability so you don't get any response.