NuTone Intercom Photo Gallery > NuTone Intercom IMA406 > NuTone Model IMA406 Control Module
The control module was the source the prmary problem with this IMA406. The muting reed switch would randomly energize onits own and the door talk relay would chatter.
The reed switch problem was solved with a few diodes and a transistor replacement.
The chattering relay was cause by a failed resistor on the terminal PCB