·Five channel host can monitor extensions (excluding confidential extensions) ·The host can call the extension and have half duplex intercom with the extension ·The host has an alarm output port, can be connected to an external microphone, and has a recording output interface ·The host and extension are connected by N+1 core wires without polarity ·Can be used in: office intercom, surveillance, toll stations, schools, factories, saunas, bowling alleys, building elevators and other places that require intercom