Ideal for wirelessly extending your doorbell system: Place the active transmitter next to your existing doorbell. As soon as it rings, the wirelessly connected receiver is activated. 8 selectable ringtones. Automatic learning code encoding. Expandable with up to 3 additional transmitters and several additional receivers. Can be used as a wireless extension for wired doorbell systems. Wireless range up to 200 m in open field. Transmitter: Infinitely adjustable sensitivity. Also works with telephones. Indicator lights for batteries and transmission function. Receiver: Infinitely adjustable volume. Sound can be switched off, e.g., at night. Visual doorbell indicator with light ring - 3 selectable colors. Battery indicator light.