Patent GB-1110992-A (GB)
Title: Automatic dialing apparatus
IPC: H04M1/274
Filed: 1965-06-21
Abstract: 1,110,992. Repertory number sender; transistor oscillators. G-V CONTROLS Inc. 21 June, 1965 [13 July, 1964; 18 Nov., 1964], No. 26192/65. Headings H4K and H3T. Fig. 1 shows a repertory number sender transmitting digits in a twoout-of-seven frequency code, but which can be adapted to transmit digit signals by connecting a combination of diodes between earth and the transmission line (Fig. 4, not shown). An oscillator, shown generally at TDO, generates two frequencies by tuning two inductances having terminals H1 to H3 and L1 to L4 respectively which when connected to a common terminal HO or LO places a capacitor over part of the inductance. The terminals are connected to two sets of common terminals G1 to G3 and W1 to W4. By permanently connecting a lead with a G conductor and another lead with a W conductor a digit is stored and by connecting the other end of the leads back to the respective common terminal of the oscillator the oscillator is tuned to transmit that digit. Four groups of three pairs of leads are shown representing storage positions for four three digit numbers, for example the first left-hand group has pairs of leads 113-114, 213-214, 313-314, the permanent connection with the common conductors being shown by a black dot. Selection of one of the groups is made by relays 11, 21, 31 or 41, one of which is operated by a controller CS by priming one of wires 10, 20, 30 or 40. The storage groups may be combined to accommodate a number having more than three digits, as shown by the two right-hand groups 133-134... and 143- 144 . . ., the relay 41 for the second group being automatically operated when the digits stored by leads 133-134, 233-234, 333-334 have been transmitted. To transmit each digit in turn after a group has been selected, pairs of leads are connected in sequence to the common terminals of the oscillator by means of three common relays 170, 270 and 370 which are operated in turn by a counter SS. The three S.C.R's in the counter are connected to a common conductor K and the first one 51 is fired as a number is selected by switches 13, 23, 33 in the controller CS. The ensuing fall in potential of conductor K and hence of terminal 543 of a pulse generator PG starts the generator producing 50 m.secs positive pulses, separated by a 50 m.sec. pause. After the first pulse the succeeding two pulses fire the second and third S.C.R's. The outputs of the S.C.R's. lead to the relays 170, 270, 370 which accordingly operate at 100 m.seo. intervals. For 50 m.secs. of each interval the positive pulse of the generator primes the oscillator to generate the two frequencies to which it has been tuned by the non- connected digit store leads. If all the three digit positions provided in a group are not used as shown in the extreme right-hand group, a muting conductor M provides for the oscillator to be disabled. Fig. 2 shows the pulse generator PG. When there is positive potential upon terminal 543 (provided by conductor K before the counter SS is started) the generator is shut off by maintaining transistor 501 conductive. Capacitor 504 is discharged with both plates held at negative potential and transistor 502 accordingly held non-conductive. Upon the removal of positive potential from terminal 543 (provided by conductor K as the first S.C.R. 51 fires) transistor 501 turns off and allows capacitor 504 to charge via resistor 512 and the transistor 502 so turning it on, and continues charging until it reaches the intermediate potential at 533, whereupon current is diverted through diode 520 and the transistor turns off. The capacitor 503 is now no longer held in a discharged state over diode 517 and resistor 515 and charges so turning on transistor 501 until the capacitor voltage reaches the potential at 533 when the transistors again switch. The terminal 541 goes positive with respect to terminal 542 when transistor 502 turns off and remains near 542 when transistor 502 is on. Fig. 3 shows an oscillator for simultaneously generating two frequencies. Transistor Q 1  has two ferrite-core transformers to produce the requisite feedback and across which are connected a capacitor Ca or Cb by connecting the common terminals Ho, Lo to one of the others by means of the circuits storing the digits. The transistor operates on the linear part of the characteristic and amplitude limitation is provided by varistors RVa and RVb. The oscillator is shock excited into oscillating by opening contact U of relay 87 to interrupt the flow of current through the tertiary winding which had been placed across RR and R of a conventional network associating the telephone set with the line N 1 N 2 . Contacts Z, V of this relay disconnect the transmitter T from the line and places a resistance R 3  in series with the receiver E during frequency transmission. Contact X of relay 88 disables the oscillator.