Offering wireless doorphone with following functions: - Wireless Doorphone GP-MA400 has the functions of wireless intercom and remotely opening door. - It overcomes the limitation of the wireless doorbell and access control system which can not talk, can not open door remotely, and avoids the trouble of run cables indoor. - It is an update substitute for the traditional doorbell. It is suitable used in family, small or medium-sized office.* Product Features: 1. Full duplex audio between Call Station and Handset. 2. Communication range is up to 100 meters in free range space. 3. Easy installation and run cables is not necessary. 4. System is fully expandable up to maximum of 4 Handsets. 5. Callers are transferable between Handsets. 6. Used with Door-releaser can open electric lock remotely by Handsets.