A receiver which controls three receptacles

This project is hidden in a bookshelf and usefully controls lights which otherwise would have inaccessable or no switches.

This is the inside. The circuit and relay boards shown are scrunched into a two-gang receptacle box. One socket is not switched and is used for the transformer which powers the receiver and the relays.

Here is the system diagram:

Here are the circuit diagrams.
Atypically it is programmed, and has a diagnostic output, via a standard DA-9S connector. Most of my projects just have a header for programming. The protection circuit is in an adapter.

Here is the program code.