[ Easy to Use with Detailed Manual ] This home intercom system have features include Monitor, Talk, VOX (Voice Operated Exchange), Group, and Calling function. Increase/lower volume too! This intercom system is easier to use than others with user-friendly multi-functions and included step-by-step instructions! [ Supported by Power Bank for Outdoor ] This home intercom system is compatible with Power Bank (5V 1A) making it easy to take these intercoms any place you want. Besides, it designed with back hole for wall mounting.