One comment to all WE 2872 Touch-A-Matic users:

DO NOT connect your TAM power to the system voltage from the KSU. One of the sides of power supply within the TAM has a jump wire to a phone line (T or R side, not sure).

So the transformer 13.5 VAC coil should be a true isolated (free floating) coil. Otherwise it can cause issues within the system.