GB1315079A - Meter pulse generator - Google Patents

Abstract

1315079 Automatic exchange equipment; transistor pulse oscillators PYLON ELECTRONIC DEVELOPMENT CO Ltd 19 April 1971 [2 April 1970] 24486/71 Headings H3T and H4K Metering pulses are supplied in a telephone system by a system comprising at least one pulse generator 12 which supplies regular pulses to a bi-stable circuit 20 producing a square wave output on one terminal which supplies a monostable circuit 23 and a shift register 24 which shift register has a plurality of outputs which are gated by the output of the monostable circuit to provide pulses in a predetermined sequence to operate associated relays whose contacts connect a voltage source to a telephone line to provide a pulse which is used for metering. The number of pulses received depends on the duration of the call and different day and night rates of pulses are provided by means of rate control 14 which in the absence of a control signal includes the frequency halving circuit 16 in the system. Preferably the inverted output of the bi-stable 20 is used to provide a "six phase" output, i.e. a sequence of interleaved pulses on six lines. In the system described the relays have two sets of contacts in the lines. Pulse generator 12 consists of a relaxation oscillator using a unijunction transistor whose frequency can be altered by varying tap 75 on potentiometer 82. The frequency may be trimmed by variable resistor 95. The output frequency of the generator can be further divided by 10 or 100 by units 102, 105. A monitoring arrangement is provided to give an alarm indication if loss of pulses is detected. Each relay board (Fig. 4, not shown) is connected to a monitor board (Fig. 5, not shown) which consists of a plurality of resettable trigger circuits each connected to be set whenever a respective relay operates. A clock arrangement provides an initial resetting pulse to the trigger circuits and, after a time sufficient to allow all the circuits to have been set, an interrogating pulse is sent to a gate (NAND logic is used) which will open to operate and alarm indication if one of the trigger circuits has not been set.