Answer door or gate from any telephone, up to 2 entryways, distinctive tone for each entry, built in call waiting, 2 way communication, up to 4000' distance with Cat5 twisted pair cable, connects to 2 line/PBX/key stations, use with dp29sw to open the door with the phone, use with dp29im to convert phone network into an intercom system, use with dp29ci to use chimes, lights or cameras, plus into AC wall outlet.