Bell Black M719S Multi-door Switching Unit

This unit allows the operation of a door entry system from two entrances. Several units may be combined to extend operation up to a maximum of eight entrances. When a telephone is called from a given entrance, the switching unit connects the telephone to the speech unit of that panel only for a fixed period (adjustable 25-230 seconds). During this time pressing the lock release button on the telephone will operate the lock of the calling door only. Boxed.