If you use the Wireless Visitor Announcement System to find out immediately if someone s approaching your home or business, or if you have the 3 Channel Receiver Chimebox w/Relay installed to trigger a relay when the Wireless Visitor Announcement System is activated, you can manually trigger this system to react using the Wireless Handheld Transmitter. Press the button on this battery powered device to activate a chime tone and/or trigger a timed relay output, which can be used to initiate an alarm for your security system, integrate with your automation system or any specialized function. This transmitter is powered by 2 AA batteries sold separately . This wireless transmitter is compatible with the Optex Wireless 2000 Annunciator System. Use it with the RC 20U, TD 20U, TR 10U and TC 10U.