Patent GB-776969-A (GB)
Title: Improvements in or relating to telecommunication systems
Inventor: ALLUM ROBIN DEVENISH
IPC: H04Q3/00
Filed: 1952-09-19
Abstract: 776,969. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. July 17, 1953 [Sept. 19, 1952], No. 23517/52. Class 40 (4). Inter-exchange switching facilities are provided in a system including the exchange described in Specification 765,925. In that exchange the group selector common control GSCCE discriminates between local calls and junction calls. In a junction call, an outgoing junction common control OJCC is seized over a path indicative of the junction group required. Routing and numerical digits are transferred from the group selector common control GSCCE (to which exchange and numerical digit had previously been transferred from the register) to the outgoing junction common control OJCC and a pulse is applied from GSCCE via the calling register to the trunk connecting circuit to mark all accessible free paths through the group selector as described in the prior Specification. A high-speed hunting circuit in OJCC takes into use a free bothway junction connecting circuit JCC in the required junction group and in a free path through the group selector secondary. A register connector searches continually for a junction connecting circuit JCC seized by the control OJCC and, on finding one, associates it with the first free outgoing junction register which accepts the information offered by the outgoing junction common control OJCC. The control OJCC is released, the information is pulsed out over the junction, the register releases and the speech path of the calling party is connected to the junction. Delay circuits are denoted by references PD and invertors by PC. High tension is provided by reset equipments RC. Group selector common control GSCCE, Figs. 1, 2. When the common control is seized by a register REG, tube VK1 strikes and pulses the exchange digit stores of all exchange digit registers through VN1, VT1, VT2 and VT3 after a delay and an inversion. The digits are then transferred from the register to exchange digit stores EDS to EDS3 in GSCCE. The exchange digit store tubes are connected (in the case of EDS1 through repeater tubes VK3) to pairs of tubes such as VK4, VK5 in a coding field to translate the exchange digits into routing digits and a meter fee marking. Each pair of tubes is connected via isolating diodes to a tube in each of six 10-tube routing digit stores RDC1 to RDC6 and to a tube in the meter fee store MFC. When the routing digits are stored, the same pulse from VK5 is applied to tubes VT5 to VT8 and orders the transfer of the numerical digit from the register to stores NDS1 to NDS4. The routing digits determine the outgoing junction group by marking and firing a pair of tubes VT9, VK6 in another coding field. Rectifiers MR1, MR2 isolate the different groups of tubes which may mark the same junction group. Outgoing junction common control OJCC, Fig. 3. The tubes VK7 to VK8 represent different junction groups. When VK6 strikes in GSCCE to identify the routing digit, a pulse over OGL strikes VK7 and a hunting operation follows in HC1 to find a free junction. In the meantime, diode VN4 strikes VK9, the tubes VK9, VK10 being identified with different impulsing speeds 10 i.p.s. and 30 i.p.s. respectively. Tubes VK11 to VK12 are allotted to the junctions which are marked free on leads MJF from the group selector secondary switches GSS. The tubes strike rapidly in sequence until a tube backed off by the free marking fails to strike. The corresponding tube of series VK13 to VK14, strikes and seizes the junction by firing a tube in the group selector secondary switch GSS over lead SJL. Diode VN5 pulses the six routing digit stores RDS, the four numerical digit stores NDS and the meter fee storage circuit MFS which accept the information offered by GSCCE in readiness for transfer to an outgoing junction register. At the same time a pulse over lead CCR signals a reset circuit RC1 which momentarily disconnects H.T. from the tubes in the group selector common control GSCCE which is released. The reset circuit is operated by the time throw-out circuit TTO1 if an unused or barred number is dialled. The outgoing junction circuit is released later when a pulse is returned over lead DRL by an outgoing junction register and, after a delay, operates reset circuit RC2. Time throw-out circuit TTO2 operates RC2 if there is no free junction or no available outgoing junction register. When there is no free junction, tube VK15 strikes at the end of the hunting operation and TPC transmits two pulses over lead JBL to step the tone control counter circuit described in the prior Specification, so as to provide busytone. Multivibrators MV1, MV2 control the impulses over leads AIL, BIL (start break periods), and IDL, PDL (end break periods) in junction connecting circuit JCC and in outgoing junction registers. The impulses controlled by MV1, MV2 have speeds of 10 i.p.s. and 30 i.p.s. and make/break ratios of 2 : 1 and 1 : 1. Seizure of junction connecting circuit JCC by register connector common control RCCC, Figs. 4, 5, 6 and 7. A 10-way pulse distributer PDC and a 10-way bias distributer BDC in a common control RCCC are provided in common to 10 register connectors RC, Fig. 5, to search over a 100 junction connecting circuits JCC for the selected junction and to allot a free junction register JREG. The counting chain VK20 to VK21 is driven by negative pulses fed at 10 to VT12. The pulses are repeated over leads CPL by tubes VK22 to VK23, each pulse being fed to 10 junction connecting circuits. Counters VK24 to VK25 in the bias distributer BDC are driven by VK23 as it fires once in each PDC cycle. Bias is fed sequentially over 10 leads CBL one tube on each of 10 junctions being primed over each lead. When the seized junction is found, a signal over RSL primes VK26 and stops the scanning by blocking VT12. After a delay reset circuit RC3 resets the common control RCCC. Register allotter. The signal from JCC over RSL, after a delay also starts the hunting chain VK27 to VK28 of a high-speed 10-way register allotter AC. In a free register JREG the first tube VK29 is conductive in a sequence counter comprising 10 tubes VK29 to VK34. The signal on RSL strikes VK30 in each register. The allotter tubes corresponding to free registers are backed off and the hunt stops at the first backed-off tube. The register is seized when VK35 strikes. Register operations. As VK35 strikes, VK26 strikes in the register connector RC, the digits stored in the junction common control OJCC are transferred to the stores RDT(1-6), NDT(1-4) a metering fee marking is transferred from MFS in OJCC to store MFT and the impulse speed marking on tubes VK9, VK10 is transferred to tubes VK36, VK37. A pulse over lead DRL signals the outgoing junction common control OJCC that the register has been seized. The sequence counting tube VK31 responds to seizure and tube VT13 is cut off to start a timing operation being conductive along with VK29 or VK30. Negative metering pulses from MPG in OJCC are repeated as positive pulses by VT14. When VK40 strikes 100 m.s. after seizure the pulses are repeated to the junction connector circuit JCC over tubes VK45, VK59 and lead MFL. The counter MFP counts from the tube marked by MFT in accordance with the metering fee. At the end position of MFP, VT14 is biased to stop the pulses. Digit sending. First-digit tube VK32 operates with VK40 and the first routing digit is transferred from routing digit store RDT1 to digit sender store DSS. Pulses from multivibrators MV1, MV2 are fed over leads AIL, BIL to repeating tubes VK41, VK42 only one of which is enabled by VK36 and VK37 in accord-. ance with the impulse speed required. The pulses are fed through VT15 and one of the tubes VK50, VK51, the make/break ratio being governed by the H.T. on leads PDL. The pulses are transmitted to the junction connector JCC over VK52 and lead DSL being counted off by a counter DSC in accordance with the digit stored in DSS. Tube VT15 is biased-off at the end of the count. In the meantime pulses are repeated by VN16 to VT13 which is cut-off at the end of each pulse. Tubes VK40, VK39, VK38 are arranged to strike 100, 150, 500 m.s. after VT13 is cut off but there is insufficient time between consecutive pulses. At the end of a digit, however, VK40 strikes and steps the sequence counter to transmit the next digit, and VK58 ensures that both VK43 and VK44 are extinguished. Transmission cannot start pending an inter digital pause determined by the appropriate delay tube VK38 or VK39 which strikes VK43 or VK44 and enables one of the tubes VK50, VK51. When all the digits have been transmitted VK56 is no longer backed off over a tube VN19 in DSS and fires to operate the reset circuit RCG and to re-operate the first tube VK29 in the sequence counter. Bothway junction connecting circuit, Figs. 8, 9. When an outgoing junction is selected by HC1 in OJCC, a voice frequency signal is applied on the P-wire through the group selector secondary switch GSS and transformers TR1, TR2 to strike VT17, VK61, VK62 and to extinguish VK60, VT18. Tube VK64 strikes, following VK61 and relay SW completes a loop over the junction JUN. Tube VK63 responds to scanning pulses on CPL from the register connector common control RCCC. Tube VK80 strikes at a coincidence between pulses on CPL and CBL and primes VK26 in all register connectors RC as described. When the register is allotted and VK26 strikes in RC, VK65 is struck over lead BTL and VK63 is biased off to prevent further seizure. Metering pulses on lead MFL step the tubes of a chain storage circuit MFM. The digits pulsed out by the junction register on lead DSL are repeated by VK69 under the further control of H.T. on IDL from a multivibrator in OJCC, Fig. 3, and are sent over the junction by VT18 and relay A. The speech circuit is completed by VK70, VK71 and relay C when pulse transmission starts. Battery reversed on reply operates relay G which enables VK73 to repea