Patent GB-840297-A (GB)
Title: Improvements in or relating to apparatus for indicating the condition of an adjustable device
IPC: H04H1/00
Filed: 1958-09-30
Abstract: 840,297. Exchange systems combined with other signalling systems. WESTERN ELECTRIC CO. Inc. Sept. 30, 1958 [Oct. 7, 1957], No. 31125/58. Class 40 (4). In a system for determining how many of a plurality of television sets are tuned to a particular channel, a signal of a frequency allocated to that channel is applied to the telephone lines of the substations, at which television sets of the plurality are located, the tuning of a set to the particular channel causing a circuit tuned to the corresponding frequency to be connected to the telephone line, whereupon the enhanced current flow at the signal frequency is rectified and operates a relay at the substation which connects an inductive shunt across the line to bring up the line relay at the exchange. In the Figures a " make " contact of a relay is indicated by a cross in a lead, and a " break " contact by a short straight line perpendicular to and crossing a lead. Contacts of a relay which appear in a Figure other than that in which the relay is shown are prefixed by the number of the Figure which shows the relay, e.g. contacts 5-G1 (Fig. 3) are contacts of relay G1 (Fig. 5). When a subscriber sets the channel selector (not shown) of his television receiver to a particular channel the switch 64 (Fig. 3), ganged to the channel selector, connects the corresponding one of the four tuned circuits 13 to 16 in series with the rectifier bridge 26 across the output of amplifier 27 which is energized by the on-off switch of the television receiver. In order to determine the number of receivers which are tuned to a particular channel one of a number of data-gathering service subscribers causes the connection at the exchange of the corresponding one of the four voicefrequency oscillators 9 to 12 to the group of line circuits concerned via transformers such as 2. If the tuned circuit corresponding to that oscillator is connected up at a substation the current flowing therein is rectified and operates the relay CM which connects the choke 31 across the line to bring up the line relay L1. For the duration of the test the line relay contacts are disconnected from the exchange equipment by transfer relay contacts such as 5-G1, and are connected instead to resistors 4 so that the currents flowing therein are summed in resistor 67 to give a reading on the meter 7 indicative of the number of line relays operated in the group. This reading is recorded by the automatic camera 8. As shown, the line relays L1 to L9 and their associated lines are divided into three groups, which are tested sequentially under control of the apparatus of Figs. 4, 5. Each group may include up to 1000 lines, it being arranged that less than a critical number of lines in any one cable be included in the same group in order to avoid objectionable cross-talk to lines engaged in conversations. Control equipment.-Each of four datagathering service subscribers A, B, C, D has an equipment 32 (Fig. 4), the four keys NLK1 to 4 of which correspond to the four oscillators 9 to 12 (Fig. 3) and to the four television channels. To initiate a test for the first channel, one of these subscribers either operates key NLK1 or key LK1 in the power supply of the automatic timer 17. The operation of NLK1 or the closure of contacts 35 in the timer brings up start relay ST1, and, provided none of the preference relays P2 to P4 is operated, P1 comes up, lighting lamp 139 (Fig. 5). ST1 also brings up the off-normal relay ON (Fig. 4), thus energizing the upper and lower windings of TT which remains cooperated, and energizing the oscillator 9 (Fig. 3). After capacitor 53 (Fig. 4) has been charged following the operation of ON, relay OT pulls up, followed by test group No. 1 relay TG1 (Fig. 4) and transfer relays G1 to G5 (Fig. 5), the group No. 1 lamp 59 (Fig. 5) being lit. Operation of TG1 connects the output of oscillator 9 to the lines of test group No. 1, and meter 7 registers the number of sets tuned to channel one, as described above. Operation of TG1 also brings up test group check relay TGK which removes the short-circuit from capacitor 71 in the biasing winding of relay TT. The charging current of 71 initially prevents TT from operating, but after a delay sufficient for the operation of the slowest line relay and the stabilization of the movement of meter 7, the relay TT pulls up and operates test group end relay TGE which' operates the automatic camera 8. TGE also holds TGK1 (Fig. 5), operated by the transfer relays G1 to G5, and operates stepping relay B1 (Fig. 5) which releases TG1 (Fig. 4), followed by G1 to G5, the CM relays and line relays operated, and TGK. Lamp 59 (Fig. 5) is extinguished. The discharge of 71 (Fig. 4) restores relay TT, whereupon TGE, and TGK1 (Fig. 5) are released, and Cl comes up in series with B1. Test group No. 2 relay TG2 (Fig. 4) then operates and the sequence described for test group No. 1 is repeated for test group No. 2, after which it is repeated again for test group No. 3. The operation of C3, which then occurs, brings down OT (Fig. 4), locks all the operated ST relays, and operates reset relay RST-1, and release count relay RC (Fig. 5). The last-named relay releases B1 to B3 and C1 to C3 (Fig. 4), whereupon ST-1 is released, capacitor 53 re-charges, and RC (Fig. 5) is released. Provided no other ST relay is operated, ON (Fig. 4) releases and the control circuit is restored to normal. If ST relays are operated the lowest-numbered of the associated P relays takes control. Interference with telephone service. Busy lines are not tested as contacts HM (Fig. 3) disconnect them from the transformers 2 and line relays L. Similarly operation of contacts HM to complete a call to a subscriber disconnects the testing equipment. A subscriber initiating a call during a test is delayed until the transfer relay concerned is released. The delay amounts to a fraction of a second and is not noticed by the subscriber. Such a call would appear falsely in the summing circuit as an operation of relay CM, but the probability of a call occurring during a test period can be calculated and allowance made therefor. Fault alarms.-Faults which would interfere with normal use of the telephone line or would seriously inpair the validity of the test cause a signal to be given on conductor 79 (Fig. 5) to the exchange alarm circuits 95 as a major alarm. For example, failure of one of relays TG1 to TG3 to operate, thereby omitting a test group, prevents operation of TGK, thereby stopping the test. If the test is not completed in the usual time capacitor 148 in the timing circuit of Fig. 5 is charged sufficiently to cause tube 81 to fire, whereupon relay TM operates. Normally C3 operates and opens the circuit of TM before tube 81 fires. The operation of TM brings up alarm relay TA which applies the signal to conductor 79 and brings up TGE which prevents further operation of stepping relays B1 to B3 and C1 to C3, thus allowing the faulty test group to be identified. TA also brings down TG1 to TG3 to prevent interference with the telephone service. When the fault has been cleared, the normally-closed non-locking key NLK8 in the holding circuit of TA is operated to release TA and cancel the alarm. Minor faults such as the failure of a transfer relay are signalled over conductor 84. In a test group of 1000 lines, 100 transfer relays would be provided each having ten transfer contacts and one checking contact, so that the failure of one relay would affect the test on ten lines only. If through the failure of a transfer relay, TGK1 does not pull up when TG1, TG2, or TG3 operates, the corresponding alarm relay AL1, AL2 or AL3 will be energized to operate the minor alarm in alarm circuit 95. After the fault is cleared, the operated alarm relay is released by the corresponding key of NLK5, NLK6, NLK7.