Long Range Wireless Intercom Phone SystemWireless intercom system, no telephone wires needed, save your phone bills. Clear Voice and Secure Digital Communication. 433MHz working frequency,anti interference signal. It needs no installation nor an installer,simply plug and use. Built in rechargeable battery,works with or without electricity power,standby time 30 days. Long communication distance up to 500m (depending on the environment). Can be placed on desk or mounted on any surface,