Patent GB-1040446-A (GB)
Title: Improvements relating to automatic telephone exchange systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q11/04
Filed: 1962-06-15
Abstract: 1,040,446. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. May 22, 1963 [June 15, 1962], No. 23164/62. Heading H4K. In a system having main and subordinate exchanges interconnected by T.D.M. channels using P.C.M., the main exchange is so programmed that pulse positions for the " go ' and " return " channels are chosen at the main exchange in such a manner in relation to the time delays on the inter-exchange lines, that at the subordinate exchange the same pulse positions may be used for both the " go " modulator and the " return " demodulator. The invention is described in relation to a " sectionalized " system of the type described in Specification 989,336 in which the call may be set up through any of a plurality of sections of equipment, the possibilities in each section being explored and the final choice of section or sections being determined by the amount of traffic currently being handled by these sections. Figs. 1, 4 show a satellite exchange A and part of a satellite exchange B interconnected with a main exchange, part of which is shown in Figs. 2, 3, 5, 6. Each satellite such as A comprises four sections WA ... ZA interconnected to corresponding sections W, X, Y, Z (the last two not shown) at the main exchange. Similary the sections WB ... ZB (of which only the first is shown) of satellite B are interconnected to the sections W, X, Y, Z of the main exchange. The interconnections comprise four time division pulse code highways such as J1/W/WA ... J4/W/WA the first and fourth being used for signalling and the second and third for speech incoming to and outgoing from the main incharge. Setting up of call.-A calling subsection LCA is detected by a scanner SCA associated with scanning gates SGA and the identity of the calling line is signalled over J1/W/WA to the main exchange where it is interpreted by circuit SD1/W and fed to common control equipment CC (not shown), which thereupon supplies, together with other relevant setting information, the identities of possible conversational routes between main and satellite exchanges to the translator TRW. The latter translates these into pairs of pulse positions suitably staggered with respect to each other to take into account the pulse transit times between the main and satellite stations on the inward and outward paths so that at the satellite the same gating pulse may be used in both directions. These pulse positions are fed to the route choosing means RC1/W. RC4/W is similarly fed. Route choosing means RC1/W, RC4/W are associated respectively with the channels outgoing to section WA, and with channels leading to registers such as RA1/W. Route choosing means RC1/W also receives information, via J1/W/WA and SD1/W, of the conditions of links between primary and secondary cross-point switches A/WA, B/WA at the satellite; and also from stores 1CS1/W, OGS1/W at the main exchange information indicative of the multiplex channel availability. RC4/W also receives indications from similar stores as to register availability. Circuits RC1/W, RC4/W then choose an appropriate route and signal the identities to CR1/W, CR4/W, respectively, which in turn signal a traffic comparator TC0 (not shown). Similar operations occur for sections X, Y, Z. The latter chooses a suitable section on the basis of the existing traffic in the sections and enables corresponding switching initiating circuits, say, SN1/W and SN4/W. These set stores 1CS1/W, OGS1/W, 1CS4/W, OGS4/W to effect connection between the chosen register and the speech paths to the satellite via one of the link pulse highways H1/W ... H5/W. The circuit SN1/W also causes marker MC1/W to transmit appropriate markings over J4/W/WA to the marker M/WA to operate cross-points in A/WA, B/WA to complete the connection. The common control circuit also supplies the register (by means not shown) with the calling subscriber's identity. Dial tone is then sent and dialled digits received. The register then signals the calling and called lines' identities to the common control circuit CC. Assuming that the call is to be made to subscriber LCB of satellite B, all relevant setting information including that pertaining to possible conversational routes between the exchanges is passed to translators. TRW, TRX ... The latter perform translations as previously described in relation to TRW and feed the routechoosers RC1/W, RC2/W which choose a route in the manner previously described whereupon the chosen route signalling circuits CR1/W, CR2/W inform the traffic comparator. Similar results are obtained from the other sections. The traffic comparator then chooses a section, say W, and enables switching initiating means SN1/W, SN2/W to complete the connection, as previously described, over one of the channels in one of the links H1/W ... H5/W. Other connections.-Connection between a satellite and a main exchange subscriber is effected over a satellite switching unit such as SSU1/W and a local switching unit such as LSU1/W. Connections between subscribers on the same satellite are completed at the satellite using a local link LL/WA, and two sections, e.g. WA, XA at the satellite, the connection being set up under control of the main exchange. Pulse gating arrangements. Figs. 12, 13, 14.- Pulse coded speech signals incoming from the satellite are received over J2/W/WA, alternate channels (each of seven positions) being gated into stores GPSD and GPSE by pulses PD1 ... PD7, PE1 ... PE7 derived from synchronizing signals received from the satellite over J1/W/WA. The stores are read out to highway HH/W in channels appropriate to the main exchange by pulses TD1 ... TD7, TE1 ... TE7, the signals being stored for a period somewhat greater than one channel period. The store 1CS1/W contains routing information, and on being pulsed in the appropriate channel position causes a decoder 1CD1/W to open one of gates G101 ... G105 to pass the channel information to a chosen one of the link pulse highways H1/W ... H5/W. For outgoing speech a set of 24 stores GPS1 ... GPS24 are provided one for each outgoing channel. Store OGS1/W is set so that on being pulsed with pulses TDM1 ... TDM24 synchronous with the channels on links H1/W ... H5/W it enables an appropriate one of gates G106 ... G153 to pass the channel information from one of the pulse link highways to the appropriate one of stores GPS1 ... GPS24 for onward transmission in the appropriate channel time. Synchronizing arrangements. Figs. 17, 18 (not shown).-The main exchange comprises a master pulse generator which provides the pulse sequences necessary for defining the pulse positions TDM1 ... TDM24 on the link pulse high. ways and the pulses TD1 ... TD7, TE1 ... TE7, T 1  ... T 7 , TP1/1 ... TP1/7, TP24/1 ... TP24/7, i.e. all the pulses necessary for speech gating except PD1 ... PD7, PE1 ... PE7. Figs. 12 ... 14. This generator also provides all the pulses for gating out the signalling conditions to the satellite over J4/W/WA. This generator also sends synchronizing signals over J4/W/WA to the satellite to synchronize a pulse generator thereat which determines the pulse positions for transmitting signals and speech over J1/W/WA, J2/W/WA from the satellite to the main exchange and for gating in received signals and speech over J4/W/WA and J3/W/WA. J2/W/WA also carries synchronizing signals from the satellite's pulse generator to a further pulse generator at the main exchange, this latter serving to gate in signals from J1/W/WA and providing the pulses PD1 ... PD7, PE1 ... PE7 for gating in the speech signals from J2/W/WA. Synchronizing a plurality of main exchanges, Figs. 20 ... 24 (not shown).-An arrangement is described having main exchanges linked by speech and signal multiplex lines (similar to those linking main and satellite exchanges) in which each master pulse generator except the first is synchronized from the master pulse generator at the previous exchange. If the exchanges are arranged in a loop it may be arranged that any one of the exchanges can control the synchronization of all the others. Reference has been directed by the Comptroller to Specification 922,798.