MONITORING SYSTEM FOR A DIGITAL TRANSMISSION SYSTEM

摘要

1. A monitoring system for a digital transmission system with intermediate regenerator and line terminal devices wherein a) telemetry telegrams are transmitted via the same signal path as the digital useful signal, but in a different frequency position, b) for the separate monitoring of the digital useful signal in both directions of transmission, two telemetry telegram regenerators are provided in each intermediate regenerator, c) each telemetry telegram regenerator attaches an individual telemetry telegram to one or more than one received and re-transmitted telemetry telegram or automatically transmits a telemetry telegram if, on the expiration of a period of time which exceeds a cycle time, no telemetry telegram has been received, d) the telemetry telegrams are constructed from two identical start blocks (S1, S2), four message blocks (M1, M2, M3, M4), where the first message blocks (M1, M2), which are identical in content, contain coded information relating to the status of the digital useful signal and where the two last message blocks (M3, M4), which are identical in content, contain coded information relating to the functions of the intermediate regenerator, from one or two end block(s) (E1, E2) e) at the receiving end the intermediate regenerators are localised by counting the telemetry telegrams and are monitored by analysing the message blocks (M1, M2, M3, M4), characterised in f) that the line terminal devices are likewise each provided with a telemetry telegram regenerator which periodically transmits its telemetry telegram at intervals corresponding to the cycle time, g) that it can be gathered from the content of the last two message blocks (M3, M4) of each telemetry telegram as to whether said telegram has been automatically transmitted or whether its transmission has been triggered by one or more than one received telemetry telegram, h) in each line terminal device a telegram receiver is provided with a store, an input device and a display device.