AIPHONE C-ML Intercom and magnetic door unlock wiring system.
Outside the building a delivery person presses the doorbell button on the LE-D unit and lets go. This rings a loud bell on the C-ML.
Inside a security person presses and holds the microphone flip switch on the C-ML and talks into it "how may I help you?" and then lets go of the switch-which in turn activates a microphone on the outdoor LE-D unit.
The outside delivery person has a few seconds to speak "your sandwiches are here!"
The indoor security person can then press the little black door unlock button which cuts power to the magnet holding the door open for a few seconds allowing sandwich to be delivered.
Alternately, a person can swipe a magnetic swipe card in the REI reader, or type in a code on the REI keypad and the door magnet will unlock for a few seconds.
With short runs of wire during testing only 3vDC was needed for the intercom and doorbell to work. I also have a 16.5vAC Revere wall wart that might work on parts of this system-possibly feeding the keyboard logic boards and magnet lock "brain" (still playing around).
"Just slide the sandwiches under the truck...meow."