Monitoring device for premises, e.g. lifts, using emergency telephone connected to public telephone network

摘要

The device monitors premises from a control station. An emergency telephone (55) located in the premises to be monitored is connected to a telephone exchange (32) of the public telephone network. The connection is via two slave devices (RD) located in the premises to be monitored and a master device (BT) located in the control station. The first slave device (RD) exchanges analog voice data with the emergency telephone (55). The master device (BT) exchanges analog or digital data with a device (33,34) providing external communication through a communication network. The master and slave devices exchange only digital data through a single internal line (45).