TM751 Transceiver - Clicking?

[Tuicemen]

The TM751 uses the first unit in the address it is set to, since your using A as the house code then the TM751 is clicking on with a receive of A1.

[Brian H]

The TM751 is hard coded to Unit Code 1
The House Code is set with the dial on the front. If you didn't reset it. It will also be on House Code A.

Motion Sensors also default to A1 for Motion Detection and A2 for Dusk/Dawn Detection.
Many times if you have changed their address. They may go back to A1 when the battery is changed.

[bkenobi]

Yup, have to set the HC and UC each time the batteries are pulled.  Pretty easy to do fortunately.