Patent GB-935220-A (GB)
Title: Improvements in or relating to multiple points with protection against short-circuitin the gates connected to such multiple points
IPC: H03K17/80
Filed: 1961-04-10
Abstract: 935,220. Monitoring telegraph exchange systems. PHILIPS ELECTRICAL INDUSTRIES Ltd. April 10, 1961 [April 13, 1960], No. 12832/61. Class 40 (3). Relates to an arrangement in which an inlet X i  is connected to a selected output Y 1 -Y 5  by actuation of an appropriate one of gates or con tacts P i1 -P i5  and is concerned with detecting if a short-circuit fault develops in one of the gates or contacts. The invention is stated to be of application in telegraph exchange systems where bivalent signals are applied to inlet X i , the signals being determined by an information source A i  which actuates a gate S i  either to allow or prevent the application of the potential of point 20. The signal elements are applied only for the period t 1  in a nine-period cycle when a gate Pi and the appropriate one of gates or contacts P i1  -P i5  are actuated. The remaining periods t 2 -t 9  are employed in fault detection. In one way of carrying out the invention, the " cocking " winding of a pulse generator 21 with memory (i.e. a generator, Fig. 5, not shown, utilizing a magnetic core so that it may be " cocked " during one period and fired if " cocked " during a subsequent period) is connected between gate P i  and the inlet X i  and is associated with gates 23 and 25, one being connected to the positive supply 25 and the other being connected to the negative supply 26. Pulse generators 27 and 28 actuate gates 23 and 25 during the periods indicated. Pulse generator 22 attempts to trigger generator 21 during the periods indicated, but is successful only if it has been previously "cocked." Generator 21 produces output pulses at 29. Detection of a short-circuit in one of the gates or contacts P i1 -P i5  is effected during period t 3  when gate 23 is actuated to prepare a circuit to " cock " generator 21 from positive supply 24 via gate 23 and any short-circuited gate contact P i1 -P i5  to the negative supply. The subsequent trigger of 21 at t 4 , if successful, produces a pulse at 29. The circuit also makes other tests. Generator 21 is " cocked " (1) at t 3  if a short-circuit occurs in gate 25, (2) at t 5  if a short-circuit occurs in gate P i  or gate 23. Pulses are then produced at 29 during subsequent triggering of generator 21 at t 4 -t 6 . Furthermore, a test at t 7  " cocks " generator 21 unless it is faulty or gates 23 and 25 fail to actuate. A pulse series is thus produced at 29 in which the presence of pulses at t 4  and t 6  indicates short-circuits and the absence of pulses at t 8  indicates a fault in generator 21 or gates 23 and 25. Generator 21 when faulty may also deliver a direct current. A circuit, Fig. 8 (not shown), separates the pulses at t 4 , t 6  and t 8  and operates alarms, or in the case of the t 4  pulses, which may indicate a short-circuit in one of gates or contacts P i1 -P i5 , maintains gate P i  inoperative so as to prevent the passage of further signals. In another way of carrying out the invention, Fig. 9 (not shown), generally similar to that described above, two pulse generators with memories are used.