A Wireless PA System is used applications where it would simply be too costly or even impossible to run
wires for a conventional PA system. A wireless PA system consists of a wireless receiver box connected to a horn PA speaker via a cable, and then some sort of wireless transmitting device, which could be a two-way radio or base-station intercom.
Someone who wants to make a page to the wireless PA system just has to set the transmitter to the same channel as the wireless PA and then press the push-to-talk button on the transmitter.
The system has a range of up to a couple of miles and the range can even be extended by adding an external antenna to either the Wireless PA, the transmitter, or both.
IntercomsOnline.com has the MURS Wireless PA System that has several transmitter options.