The AKG Perception SR 45 is a wireless receiver for use with the Perception line of wireless transmitters. To help you find an interference free channel to use, the SR 45 has 8 selectable UHF frequency bands choose from. The receiver also provides XLR and 1/4" jack outputs for connecting to your mixer and sound reinforcement system. Also, in order to suppress interference noise when the transmitter being used is turned off, the SR 45 uses an automatic squelch circuit that switches the receiver off if the received signal is too weak.