GB1004453A - Improvements relating to subscription communication systems - Google Patents

Abstract

1,004,453. Programme distribution systems. ELECTRIC & MUSICAL INDUSTRIES Ltd. Nov. 9, 1961 [Nov. 9, 1960; Aug. 22, 1961], Nos. 38412/60 and 30168/61. Heading H4R. A subscriber's apparatus in a subscription system comprises a selector for selecting programmes received in different frequency ranges over a common circuit, and metering means arranged to time the duration for which the selector is set to a particular programme. As shown the various television programmes are separated by filters 9 . . . 12 and fed over switches 22 . . . 25 to a receiver connected to the circuit 4. The programme selected by filters 9 and 12 are not metered and are connected directly by switches 22, 25. The programmes received by filters 10, 11 are metered as follows:-Each such programme is associated with a characteristic control frequency which frequency modulates a carrier accepted and detected by amplifier 29 and detector 30. Switches 18 and 19 may only be closed when a coin is inserted in the meter 26. Simultaneously a corresponding switch 34 or 35 is closed to tune the circuit 31 to the corresponding control frequency. The latter is applied in short bursts, the repetition rate of the bursts depending on the charging rate for the programme. The bursts are rectified and fed to a counter which is arranged to deliver a reset signal to the meter 26 after a prescribed count. The latter count may be arranged to be varied in accordance with the value of the coin inserted in the meter. Whilst the programmes selected by switches 22, 25 are not timed, the operation of these switches may be made dependent upon the insertion of a coin in the meter. The frequency carrying the control signals may also carry a " barker " channel. The filters 9 . . . 12 may be replaced by a series arrangement of rejector circuits from which the respective programmes are taken. Alternatively filters . may also be arranged so as to distort the signals until modified by the coin-freed meter. In the case of television signals only part of the frequency band may be normally transferred, e.g. the sound only, a band near the video carrier frequency being suppressed. Or in the case of colour television the band near the chrominance sub-carrier may be suppressed. The coin-freed meter may be replaced by one which merely assesses the amount owed by the subscriber. In a further modification separate control wires fed by D.C. pulses may be used to control the counter. Each of these wires may also carry a " barker " circuit. In the case of special programmes to be received by members of a particular class only, e.g. doctors, such members may be provided with a special key for enabling the appropriate filters. The meters for a particular group of dwellings may all be located together (in the case where the system is operated on a credit basis). The input to the counter may also be arranged to operate a relay to earth a conductor appropriate to a subscriber, which conductor is led to a central point. The control bursts for the programmes each last 10 seconds and occur at different times in a one-minute cycle for the different programmes. During the 10 seconds appropriate to a particular programme the conductors from a number of subscribers are scanned to give a count of the number of subscribers receiving the programme. Alternatively a circuit comprising a series resistance for each subscriber is provided, the counting relay shorting this resistance, so that the current flow, measured at a central station, beingused to measure the programme popularity. To provide the pricing pulses, the central station includes a motor-driven cam operating from microswitches (one for each programme) in succession. The microswitches are connected to respective wipers of four uniselectors which step once per minute. Contacts of each uniselector are connected via switches (operated manually or by punched card) to an enabling circuit for the appropriate pricing oscillator. The spacing of the contacts so connected determines how frequently the pricing oscillations are emitted.