Sam, in the continuing saga entitled "Sam & Art...separated at birth" I will tell you that I made lots-o-money going around to Dr's offices on the Upper Left Side wiring lobby intercom circuits into a spare appearance on 1A2 and later, EKTS.
This allowed the secretary and others in the office to answer lobby ICM calls from any station, and not have to run over to the ugly old lobby ICM station which was often in an inconvenient spot.
I used a 24 Vac relay to switch the ICM buzzer lead to GEN, and thence onto the Ring side of a 400D card, which operated the CMB ckt and the line appearance flashing lamp; and a 401A KTU, capacitively coupled to the ICM "T&R" of the ICM so the stations could have a balanced talk pair. (Often the lobby ICM was unbalanced.)
To do it right, it required two slots, so many times, I used a 259 KTU to get the extra slots, or replaced a shoebox with a 501.
