Patent GB-868493-A (GB)
Title: Improvements in apparatus for monitoring the use of radio receivers
IPC: H04H60/31
Filed: 1957-08-28
Abstract: 868,493. Radio receiving apparatus. NIELSEN CO. Ltd., A. C. Aug. 28, 1957 [Nov. 7, 1956], No. 27144/57. Class 40(5) A system for recording at a central station information concerning the tuning conditions of a plurality of radio and/or television receivers comprises at the central station a radio transmitter from which interrogating pulses are periodically radiated and, at each receiver, or in each home containing one or more receivers, apparatus which radiates coded information back to the central station in response to said interrogating pulses, the arrangement being such that the items of information concerning the receivers are radiated back to the central station in a predetermined sequence. The central station, Fig. 2, comprises a rotary switch provided with 240 contact segments and a wiper arm rotating once per minute. During the first quarter-second period of each minute the wiper arm engages contact 39 thereby energizing transmitter 14 which accordingly radiates a succession of pulses for the duration of the quarter-second interval. During the next 118 quarter-second intervals, reply pulses are received by receiver 30 in respect of television receivers; the information conveyed thereby is applied to a decoder 29 and thence to a totalizer 33. At the end of this interval the wiper arm engages a contact 48 to actuate printer 34 to print the information stored in the totalizer 33. The wiper arm then moves to contact 49 to reset the totalizer 33. Thereafter for the next 117 quartersecond intervals reply pulses are received in respect of sound receivers at the end of which interval the information stored in the totalizer is printed as before and the totalizer reset. This completes the minute cycle of operation of the recording apparatus. The pulses received by receiver 30 are coded with one or more of five different possible modulation frequencies according to the condition of operation of the respective receiver. These frequencies are separated out by filters 58 and applied to punched-tape recorder 32 which makes an individual record of each successive signal received. Once a minute, when the wiper arm makes contact with contact 39 a timing mark is punched by the recorder. This recording may be affected instead upon magnetic tape. Fig. 3 illustrates the apparatus provided at a home comprising a television receiver 77 and a sound receiver 78. The received interrogating pulses are applied to receiver 20 the output from which actuates relay 71 to start motor 73 rotating and driving the wiper arm of a rotary switch 76 in synchronism with the switch 35 at the central station. After a predetermined interval the wiper arm makes contact with contact 79 whereby relays 82 and 70 are actuated to energize the transmitter 24 and connect it to the aerial 18. Simultaneously the output of a coding unit 28 associated with television receiver 77 is applied to modulator 23, this output being one or more of five different audio-frequencies supplied by oscillators 114. The transmission continues for the quarter-second during which the wiper arm is in contact with contact 79; thereafter it ceases until the wiper arm reaches contact 89 whereupon a similar transmission in respect of sound receiver 78 is radiated from aerial 18. In an alternative system, the interrogating transmitter radiates an interrogating signal every quarter-second, each signal being coded, e.g. by a modulation frequency, so as to cause a response in the apparatus associated with a respective receiver. Thus a reply signal appropriate to each receiver is radiated to the central station once every minute, the signals being radiated in a predetermined sequence. In a further system, interrogating pulse is radiated at the beginning of each reply interval. The apparatus associated with each receiver comprises a counter so that each receiver initials a reply only when the appropriate number of interrogating pulses has been radiated. Specifications 819,524 and 847,596 are referred to.