Extra WR-3000 Receivers may be added to any of the 3000 systems. The WR-3000 plugs in to a standard wall outlet and can be placed on a table or mounted on the wall. When the receiver gets a signal from a transmitter one of 4 different tones (Classical, Westminster Chime, Ding Dong, Whistle) will sound for a few seconds. There is also a volume control so you can set the sound to the desired level. The receiver is also equipped with 4 form "C" relays (one for each zone) and one 12 VDC output terminal that will activate for several seconds or 10 minutes when a signal is received.