AIPHONE GT1D AUDIO 2-WIRE HANDSET STATION FOR GT SYSTEMOverview The GT 1D is an audio only tenant station for the GT series Multi Unit entry system. It is equipped with Door Release, Option, and Guard buttons. When a visitor calls, the tenant station rings and the call is answered by picking up the handset. The GT 1D also has the capability of calling the Concierge Security Guard station(s), turning on a light while speaking with a visitor at the entrance, and receiving an emergency tone from a pull cord