Improvements in or relating to a method of and a device for eliminating spurious information in a signal transmission system

摘要

824,065. Multiplex transmission systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. Aug. 23, 1957 [Aug. 23, 1956], No. 26733/57. Class 40 (4). In a multiplex transmission system arrangements are provided for eliminating spurious supervisory signals due to momentary interruptions of the main transmission path. Fig. 3 illustrates n channels obtained after demodulation and filtering of an incoming frequency division multiplex system, respective supervisory signals being received as 3825 c/s. signals over lines L1 . . . Ln which signals after detection at M1 . . . Mn operate supervisory relays R1 via their lower coils to apply positive potential to leads m1 . . . mn. In addition a group pilot signal (which may also be used for automatic gain control) is demodulated to produce over lead L a 3920 c/s. signal which is detected at M whose output kicks relay R in the released condition. In the event of a transmission failure R (which may be electronic) closes its contact rapidly to fire all tubes G1 . . . Gn whose associated relays R1 . . . Rn are at the time operated, to maintain such relays operated over their upper windings. When the transmission path is restored R operates more slowly than R1 . . . Rn to leave the latter once more under control of the 3825 c/s. signals. The invention is applicable both to systems in which the 3825 c/s. is normally present during a connection and systems in which it is normally present when no connection exists.