Custom Circuits

Can anyone give me a summary of the rules for custom circuits? They appear spread out in the manual and in many different places.

Ctrl-F is the best way to find spread out rules, but the biggest rules to be aware of regarding CUSTOM CIRCUITS are R30 (all voltages have to be less than 24V) and R44 (CUSTOM CIRCUITS can’t alter power or control pathways between key control system components).

Thanks. That’s what I needed to know.