METHOD, SYSTEM AND DEVICE FOR LINE MONITORING

摘要

The invention concerns a method, a system and a master terminal for line monitoring in system comprising a telephone network (ISDN), a master terminal (MASTER) connected to a place of reception (PR) of a response and to the telephone network (ISDN), and a slave terminal (SLAVE) connected to an object being monitored (OM) and to the telephone network (ISDN). In the method, the setup of a control call from the master terminal (MASTER) to the slave terminal (SLAVE) is started, the control call originated by the master terminal (MASTER) is identified by the slave terminal (SLAVE) on the basis of a predetermined ringing procedure before answering the call, the call setup procedure is terminated, the setup of an acknowledgement call from the slave terminal (SLAVE) to the master terminal (MASTER) is started upon the lapse of a suitable length of time after the control call, the acknowledgement call received from the slave terminal (SLAVE) is identified by the master terminal (MASTER) on the basis of a predetermined ringing procedure before answering the call, and the call setup procedure is terminated. The invention is applied in technical monitoring of a line between two points e.g. in an alarm and monitoring system.