Built-in transmitter for control by up to 4 external buttons. The transmitter fits into a switch box behind an existing button/switch, and is therefore used to expand an existing switch range with radio functionality. Due to the ability to transmit at adjustable intervals, this device is ideal for reliably transmitting long-lasting switching states (such as motion detectors, timers, thermostats, etc.). For this operating mode, a follow-up time corresponding to the transmission interval can be set on the respective radio receivers. 3 operating modes (button mode, interval transmission with 10s or 30s, only 3 transmission intervals)., Compatible products: radio receiver FE3 series, radio dimmer FD3 series, repeater FV2 R., Dimensions: 43x43x33mm, 230V AC, 4 channels