Patent GB-1023816-A (GB)
Title: Improvements in or relating to electric signalling systems
Inventor: PETHERICK EDWARD JOHN
IPC: G08B25/04
Filed: 1964-02-14
Abstract: 1,023,816. Monitoring systems. HONEYWELL CONTROLS Ltd. Dec. 14, 1964 [Feb. 14, 1964], No. 6205/64. Heading G4H. A master station and a plurality of subsidiary stations are coupled by a closed loop, each subsidiary station has a plurality of monitoring points connected thereto, detection of a change of state by a monitoring point breaks the loop and initiates scanning of the subsidiary stations to determine in which of these stations the change of state has occurred, and on such identification the monitoring points at that station are scanned to identify the monitoring point which has detected the change of state, the system then being reset to stop further scanning being initiated by that monitoring point unless the reverse change of state occurs. A change of state at a monitoring point of a subsidiary station causes the associated contact PA1-PA56, Fig. 3 (not shown) to change over. The circuit to relay A21 is broken and contact 21/1 opens the loop Y1 so that relay Z21 at the master station, Fig. 2 (not shown), drops out. Selector Z25 then energizes a combination of 3 out of 6 lines Y4-Y9 to select one of the subsidiary stations determined by the connections of relays A28-A30 to lines Y4-Y9. At the selected station, relays A31, A32 also pick up and a signal is applied to Y10 provided A21 is still energized, i.e. no change of state has occurred at that station. Relay Z29 at the master station picks up and energizes gates Z32 to pass pulses from Z35 to selector drive Z28 whereby the subsidiary stations are selected in turn until one, e.g. station A is reached at which a change of state has occurred, signified by no return signal on Y10. Z29 then drops out and Z33 picks up to control gates Z32 so that pulses are supplied to Y11 via selector Z26. These pulses advance a selector A40 at the selected station and a selector ZA50 which corresponds to this subsidiary station. The selector A40 tests the contact pairs A39/1, PA1 to A39/56, PA56 in turn, and provided the PA contact being tested has not changed over, a signal is returned over Y12 or Y13 to maintain Z33 energized. When a changed over contact PA is found, e.g. PA6, Z33 drops out and alternate positive and negative pulses are applied to pulser coil A42 over Y14 and to pulser coil ZA52 via selector Z27. The coils A42 and ZA52 are moved on a rotating arm of the associated selector so that the first positive or negative pulse applied thereto changes over the contact 39/6, ZA51/6 depending on the position of this contact. Changing over 39/6 energizes Y13 and pulsing of selectors A40, ZA50 is resumed, any other changed over contacts PA being detected in a similar manner. When selector A40 reaches its home position A21 again picks up, and if no change of state has occurred at another subsidiary station-or a recent change has occurred at station A, the system restores to normal, Z21 picking up over Y1 If another subsidiary station has broken loop Y1, Z21 does not pick up and station scanning is resumed by selector Z25. Each selector ZA50-ZT50 at the master station has associated indicators, e.g. ZA55/1 to ZA55/56 corresponding to the minitoring points of the associated subsidiary station. When a contact such as ZA5/6 is changed over by coil ZA52, a pair of green lamps, which are normally lit continuously, start flashing. The operator, by way of acknowledgment, presses a push-button which extinguishes the green lamps and lights a pair of red ones. If the reverse change of state occurs at PA6, subsequent detection of this will cause ZA51/6 to be changed back, and the red lamps start flashing. Operation of the push-button then extinguishes the red lamps and the green ones are continuously lit again signifying that PA6 is in its original position.