The doorbell host is used together with the doorbell button. Just press the button and the doorbell will receive a signal and you will know immediately that someone is coming. 5 adjustable volume levels. Strong penetrating ability High frequency transmission technology, up to 100m distance. Hign-concerned Chemical:None Connection Type:WireLess Alarm:Yes (The product appearance and printed words may vary depending on the batch, but this does not affect use) Plug Type:US Plug, it applies to Canada, India, Mexico, Thailand, Taiwan, the United States, the Philippines and so on./EU Plug,it applies to Indonesia, Germany, France, Spain, Italy and so on. Voltage:AC110V/AC100-240V Color:As Shown Material:ABS<br><br>Package Contents: 2 * buttons 2 * receivers Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.