Special Features:

Talk back flush mount substation, w/relay for handset or mic; call

Properties:

An item which may provide two-way amplified voice communications when connected to one or more like stations directly or via intermediate control equipment; includes loudspeaker (which may be used as a loudspeaker or microphone), signalling devices, amplifier and station selector switches. May include separate microphone, earphone, handset or headset. See also, telephone connecting station.