Battery-free Functional Devices WWS Series wireless switch transmitters are used to control lighting, but they can be used to control virtually any on/off device. Each self-powered wireless switch transmitter can be placed anywhere within range of a receiver. Switch transmitters are powered by EnOcean's energy harvesting technology that converts the press of the switch into a small amount of electricity. This electricity is used to transmit a wireless signal that communicates with a wireless relay receiver. The WR Series wireless relay receivers are prepackaged with relay, LED, socket, mounting rail, transient protection, and housing. The relay receiver has built-in repeater function. Relay receives signal from wireless switch transmitter and rebroadcasts the signal to the next relay receiver.