Patent GB-1089499-A (GB)
Title: Improvements in or relating to electric signal pulse recording systems
IPC: H04M15/18
Filed: 1965-10-20
Abstract: 1,089,499. Automatic exchange systems. SIEMENS A.G. Oct. 20, 1965 [Oct. 21, 1964], No. 44371/65. Heading H4K. In a magnetic drum metering pulse counting and storage system metering pulses appearing on lines 11 to xy and subject to mutilation are individually monitored by cores K11, Kxy, in a matrix AM the rows of which are read out cyclically by pulse pairs a, b, the first of which restores any core registering the presence of a meter pulse and the second switching any core that has been switched back by the continued presence of a meter pulse; cores switched by the second pulse producing outputs that are gated to register AR, where they are serially examined, and the similar results of the preceding scan and the scan before that being preserved in registers SR1 and SR2, respectively, to provide data from which the presence or absence of a meter pulse may be judged despite mutilation. The rows of the matrix may be read out by a group of three pulses a, b, c, the first pulse having the same function as before and the second and third producing a single output to the register AR for any core of the row, providing that either or both pulses switch the core. The scanning results of the group of lines read together from a row of the matrix AM are serialized by a generator TVS to provide outputs el to gate AS. In synchronism with the outputs el, the stores SR1 and SR2 are read to provide outputs e2 and e3 representing the preceding scan result and the result of the scan before that for the same line. Gate AS is an AND gate for the pulses el, e2, but is inhibited by the pulses e3, so that it passes a pulse to an ADD-ONE circuit AD if the system has judged a metering pulse to be absent once and present three consecutive scans. The cycle in which the lines are scanned coincides with presentation of the corresponding metering totals to the ADD-ONE circuit by the magnetic drum register SP. Instead of gating a simple instruction over the gate AS the address of the line judged to have delivered a meter pulse may be passed to the magnetic drum circuit for subsequent assimilation. Instead of using a single store AR two may be employed, one being read out to the gate AS while the other receives the core states of a further row of the matrix AM. Where metering is effected at a circuit which is not permanently associated with a subscriber the meter pulses are accompanied by the identity of the subscriber to be charged. To be capable of detecting meter pulses despite short interruptions in the body of the mask or space regions of the meter pulse train, or mutilations due to contact bounce at the beginning and ends of the pulses the following relationships are stated for the case of interrogating pulse pairs a, b. The spacing tD between an a and a b pulse must exceed the maximum gap produced by contact bounce. The sum of the a, b, pulse spacing tD and the maximum width of an interruption in the body of the mark or space region of the meter pulse train must be less than the spacing tF between consecutive pairs of a, b, pulses which latter spacing tF must also be less than half the sum of the meter pulse mark period plus tD and must also be less than the space period diminished by the sum of tD and the maximum extent of contact bounce or the end of a meter pulse.