Bell-219 TX noise-activated wireless transmitter for the wireless extension of doorbells. Simply place the transmitter near your existing doorbell and attach the external microphone using the included adhesive pad. Once your doorbell rings, the wirelessly connected receiver is activated. Compatible with all wireless components from the BELL and FG series by m-e. The Bell system can be expanded to a total of 4 transmitters and an unlimited number of receivers. The wireless range is up to approximately 200 meters (in open field), depending on the receiver used.