Patent GB-1148135-A (GB)
Title: Automatic dialling system
Inventor: SMITH RONALD RIGBY
IPC: H04M1/272
Filed: 1966-07-14
Abstract: 1,148,135. Substation circuits. TELOTEL Ltd. 13 July, 1967 [14 July, 1966], No. 31685/66. Heading H4K. An automatic dialler for dialling a predetermined number comprises a square wave oscillator, a first cascade counter which is incremented and successively enables each of a set of NOR gates, each associated with a different stage in the dialling procedure, and a second cascade counter which cycles for each stage and sequentially enables a second series of NOR gates. The device is intended to dial a central station at which a receiver is located and to connect a recorded message transmitter as described in Specification 1,055,186 to line. The message transmitter transmits previously entered booking information to the central station by voicefrequency signalling. As shown, the first counting chain comprises bi-stables BD1 to BD5 and is incremented once for each stage, a stage being a variable period in which, say, the pulses of a digit are transmitted, an interdigit pause or other waiting period (e.g. to allow for delay in dial tone) is timed, the transmitter is allowed to transmit &c. The outputs of the first counter are multipled on lines A1 to A10 and NOR gates G1 to G11 and G15 and D1 to D7 are coupled to these lines so as to respond to different combinations, e.g. G1 responds to the initial all zero count, G2 responds to every even count to provide an interdigit pause and D1 to D7 respond to counts of 3, 5, 7, 9. 11, 13 and 15 respectively to allow the transmission of a digit. The first counting chain is pulsed at the termination of each stage by setting and resetting a bi-stable S4. The time interval between successive resettings is determined by the second counting chain BD6 to BD12 which is driven by the square wave oscillator S5. The outputs of the second counter are multipled on lines B1 to B7. The oscillator produces pulses at the dialling pulse rate of ten per second. A NOR gate G16 is connected to the lines B1 to B7 so as to respond to a count of 120 and thus measures a period of 12 seconds. Its output is used to measure the time lag allowed between looping the line (by a relay RL1 when a key 47 is closed) and stepping to the next stage, thus allowing for dial tone to be returned. A NOR gate G17 responds to the count of 10 and in conjunction with the gate G2 gives an interdigit pause of 1 second. NOR gates C1 to C7 are arranged to respond to counts corresponding to the digits of the number to be transmitted and in conjunction with the corresponding gate D1 to D7 measure at the appropriate stage a time interval of duration sufficient to pass the appropriate number of pulses to the dialling relay RL2. A gate G4 turns on the transmitter (not shown) during the appropriate stage and the transmitter repeats its message three times and after each time pulses a line 66 to step the second counter. A gate G3 responds to the count of three which causes the line to be broken and the whole cycle to be repeated, unless a tone detector TD receives a signal from the central station indicating that the message has been received. A pair of bi-stables S1 and S2 are incremented once for each full cycle and on the count of three a NOR gate G14 is enabled to sound an alarm if the apparatus has not already been shut down by the reception of a tone by the tone detector TD.