GB678770A - Improvements in electrical systems of remote supervision - Google Patents

Abstract

678,770. Electric selective signalling systems. GENERAL ELECTRIC CO., Ltd., and POPE, B. W. April 26, 1951. [June 29, 1950] No. 16266/50. Class 40 (i). Apparatus for indicating two kinds of alarm, e.g. permanent or temporary, from a number of apparatus groups at a power station comprises synchronously stepped switches at the transmitter and receiver, two contacts in each of two switchbanks associated with each alarm point, and means for transmitting a characteristic signal, e.g. a positive potential, through said contacts to indicate at the receiver the characteristic alarm at the transmitter and appropriate apparatus group. A permanent alarm is produced by the closure of switch P, Fig. 1, associated with one particular apparatus group, causing energization of relay PR, which locks itself, and de-energizes relay ST, to break the circuit through stepping magnets S and T, Fig. 2, at the receiver, subsequently re-energized by the operation of slow-to-operate relay PS. Thus, the switch contacts S1-S4, T1-T3 step forward one step, and continue stepping in synchronism for one cycle through S4 and impulsing contact IP.. At contact 6, relay PG is energized through Sl and locks itself, while S2 transmits a positive potential to the receiver, where relays Q, QA are operated and lock themselves, contact QA2 applying an intermittent voltage to lamp LA via leads FS, FL. T1 applies the necessary positive potential to IP to cause the stepping magnets S, T to proceed one step to the seventh contact, when relay PA is energized via Sl, and S2 again sends a positive potential to T2 to operate relays QB, QC in succession, and again T1 supplies the positive potential to IP to cause the magnets S, T to complete the stepping cycle. Thus, the operation of the permanent alarm P causes all the relays to be energized and lamp LA to light intermittently. The signal is acknowledged at the receiver by the operation of key AK, when relay QA is released and lamp LA is continuously lit. The release of permanent alarm switch P initiates another stepping cycle, when all the relays are returned to normal and lamp LA is extinguished. A temporary alarm, produced by the temporary closing of switch F results in a signal from S2 at the sixth contact but not on the seventh. Thus, at the sixth contact the lamp LA is intermittently lit, but at contact 7 relays QB, QC are not operated, so that the operation of key AK causes lamps LA and RA to light steadily, the circuit being returned to normal by the operation of key RF. The signals sent from the transmitter to the receiver may be positive potentials as above, or any other method of signalling, e.g. pulses or V.F. signals.