The RL Complete Door Phone System is the perfect way to have safe and efficient access control on your premises. The easy-to-install, crisp, and clear sound intercom is perfect to get the job done the right way. Product Features: The lock intercom indoor extension: 1 (mounting bracket distribution indoor machine) Outdoor talkback host: 1 Two-way intercom and unlocking function. Two-wire connection. The outdoor machine using the new ABS plastic, durable. A lateral sound eliminating circuit excellent, clear voice intercom. The effective communication distance of 300 meters. Convenient installation, user can install The indoor machine with the lock function, someone rang the doorbell, in the indoor machine, push the button to open the lock. The outdoor machine distribution covers a, more human. Product Specifications: Audio distortion rate greater than 50mw Call time: unlimited free calls; The power adapter input voltage: AC220V 50Hz The power adapter output voltage: AC12V 1200mA Frequency response: 300 - 3400HZ + 3dB Working voltage: DC12V +/- 10% Power: static 0.2W, 2W, call state Installation: free wall