GB785885A - An electronically controlled counting device - Google Patents

Abstract

785,885. Photo-electric counting devices. HADLEY TELEPHONE & SOUND SYSTEMS, Ltd. March 14, 1956 [March 16, 1955], No. 7610/55. Class 40 (3). An electronically-controlled counting device of the kind dependent on the interruption of two light beams by objects passing through the entrance to an enclosure or vice versa is made to indicate the number within the enclosure by determining the difference between the number entering and leaving or alternatively to indicate the difference between the capacity of the enclosure and the number of objects in it. In the embodiment described, which relates to the indication of the number of vacant seats on the upper deck of a bus, photo-conductive cells PE1, PE2 are energized by horizontal light beams X, Y in close proximity produced by the reflexion from mirror 7 of light beams originating in lamp 5 ; the cells are shielded from the lamp by screens 8, 9. When light to cell PE1 is cut off by a person entering light beam X the resulting control grid potential of valve V1 rises, causing operation of relay MR1, thus closing contact 1a and opening contact lb. The subsequent blocking of light to cell PE2 by the passage of the person causes relay MR4 to operate, thus closing contact 4a and the restoration of light to cell PE1 causes the reclosure of contact lb, the slow release of relay MR4 due to capacitor C2 allowing a signal to pass to terminal B of an electromagnetic counter, used as an indicator, such that one is subtracted from the number of vacant seats shown. After a person's passage in the reverse direction a signal passes through contacts 3b, 2a to terminal C, thus causing an addition of one of the number indicated. A limit indicator illuminated by the closing of contacts SW when no vacant seats remain, may be provided.