Patent GB-935371-A (GB)
Title: Improved interrograting and recording system
IPC: H04N7/173
Filed: 1959-12-16
Abstract: 935,371. Electric selective signalling systems. SKIATRON ELECTRONICS & TELEVISION CORPORATION. Dec. 16, 1959 [Dec. 17, 1958], No. 42815/59. Class 40 (1). A monitoring system for a subscriptiontelevision service is described in which the television receivers are scanned by a central station about once every ten minutes and a record is made (for subsequent use in an accounting machine) of the particular television programme being received by each receiver. In each of the embodiments described the system is controlled by record cards, a call-word being read from a record card to select and interrogate a group of television receivers which then return indications of the particular programme being received by them to the central station where they are punched into the same record card from which the call-word was read. In the first embodiment, Fig. 1, the television receivers are arranged in fifty reply groups, each reply group having its own individual reply lead connected back to the central station. The receivers are also associated in a number of accounting groups, each accounting group comprising fifty television receivers one from each of the fifty reply groups and being associated at the central station with an 80 column x 12 row record card in which is punched in columns 1 to 20 the call-word for the accounting group and in columns 31 to 80 indications of the particular programmes being received by the television receivers at the time the call-word is transmitted. Fig. 2 shows a typical record card for use in the system described with respect to Fig. 1, which operates as follows: a record card is fed from a stack of cards 34 to 18 reading brushes 44 which enter the call-word (see Fig. 2) into a buffer store from where it is read by timing pulses from the television synchronizing unit. The four bits of the call-word then cause a selected four oscillators to operate in succession applying a serial combination of frequencies to a line 70. These frequencies are then amplitudemodulated on. to an appropriate carrier and mixed with the television programmes (X, Y and Z as shown) and transmitted by coaxial cable to all the television receivers in the system. Of those television receivers operating those in the accounting group corresponding to the transmitted call word respond and send back to the central station, on their individual reply leads, indications of the particular programmes being received. The individual reply leads, only two 162, 166 being shown in Fig. 1, are each connected to a reply detector, and the programme indications take the form of a particular frequency for each programme. As described, it is assumed that television programme Z is transmitted free of charge so that records are only made of those receivers which receiv programmes X or Y. Programme X has an associated indication frequency of f1 and programme Y a frequency f2. An interrogated receiver transmits the appropriate indication frequency back to the central station where it passes to a reply detector (only reply detector No. 50 being shown in detail) to enter a " one " in an appropriate bistable store. The outputs from these stores pass to two rows of 50 punches, one row for each of the two programmes X and Y, which under the control of timing pulses synchronized with the card feed mechanism, punch in the record card holes corresponding to those television receivers actually receiving the two subscription programmes X and Y at the time when the call word is transmitted, as shown in Fig. 2. In order to increase the capacity of the system multideck record cards may be used and record cards having two and three decks are described. In order further to increase the capacity of the system, that is to increase the number of television receivers that can be interrogated in a given time, additional card readers and punchers must be used and the second embodiment, Fig. 10, describes a threemachine system. This system differs from the system shown in Fig. 1, in that it has three readers and punchers and three associated buffer stores (for call-words). Only one set of 18 oscillators and one set of 50 reply detectors, as in Fig. 1, are used and these are shared among the three machines by means of a " priority " determined circuit, which is basically a dis. tributer ensuring that those television receivers called and interrogated by a word from machine 1 (for example), have their indications punched in the card in machine 1. The reply detectors, for example, No. 50, are however modified to the extent that each includes three pairs of stores (and not one as in Fig. 1), that is one pair per machine to allow for the appropriate buffering of reply signals before they are punched. The system also differs from that described with respect to Fig. 1 in that a fivebit call-word (instead of four) is used. The priority determining circuit is described and claimed in Specification 935,376, and receives a pulse on a lead 284, 286 or 288 whenever a machine has read a call-word into its buffer store. It then produces a pulse on the appropriate one of lines 276, 278, 280 which causes the read out of the associated buffer store, the interrogation of a selected 50 television receivers and the storing of their replies in the appropriate stores in the reply detectors. The subsequent read-out of these stores and card punching is done under the control of clockpulses produced by the machine in question. The priority determining circuit also has the property that if signals arrive substantially simultaneously on two or three of the leads 284, 286, 288, indicating that two or three of the machines are ready to interrogate selected field stations, then machine No. 1 takes precedence over No. 2, which in turn takes precednece over No. 3, and this determines the order in which the output signals on leads 276, 278 and 280 occur. A checking circuit for checking that the correct number of frequencies are transmitted in each call-word is described in Specification 935,375, which is referred to, and .detailed descriptions of reply detectors and of a call-word recognition circuit for use in the television receivers, are given in Specifications 935,374 and 935,372, both of which are referred to. The description in Specification 935,373, which also is referred to, is identical to the description in the present application, but the claims differ.