The T-6715(D) is a IP intercom control unit for a economy solution, which is separate the network audio adapter and intercom panel, thus each adapter could connect eight intercom panels to save cost. It is very reliable industrial two way communication system for bank, prison, hospital, school, mining plant, transportation center, airport, metro or subway. In a real applications, there will be several network paging microphone T-6702 shall used as duty service for reception desk, information desk, security offer, nurse room or logistic center. Each duty network paging microphone will be ID address distinguished by its own IP address, so one duty network paging microphone shall be responsible to answer and supervise several IP intercom panel T-6716(D) or T-6717(D). Under emergency or information inquiry, the IP intercom panel can press button to call to its pre-designated duty microphone, the duty microphone can answer or reject the call. If the pre-designated duty microphone is long time no answer or busy, the secondary duty microphone will be automatically transferred. Every ring call is accompanied with warning chime tone and flashing indicator. While the duty microphone with could directly make announcement or send pre-recorded messages to the IP intercom panel to warning the potential emergency which may be saw from CCTV system.