Patent GB-1123571-A (GB)
Title: Improvements relating to automatic telecommunication systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/545
Filed: 1965-08-18
Abstract: 1,123,571. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 29 July, 1966 [18 Aug., 1965; 10 Jan., 1966], Nos. 35437/65 and 1132/66. Heading H4K. A multistage switching network has on one side terminals connected to lines and to all auxiliary equipment (such as registers and supervisory tone sources), while the terminals on the other side of the network are connected solely to link circuits; a common control setting up connections across the network between a terminal on the one side to a chosen link circuit and back from the link circuit to another terminal on the one side; the establishment of a connection between a calling and a called line involving at least one connection between the calling or called line and a piece of auxiliary equipment. A typical connecting sequence is shown in Fig. 2, where a calling line is first connected over paths A1, B1, C1; A2, B2, C2; and a through link TL to a register REG. When sufficiently acquainted with requirements REG asks for the paths A3, B3, C3; A4, B4 C4; to a ringing circuit RC (fully described with reference to Fig. 16, not shown), and the further paths A5, B5, C5; A6 B6 C6; to connect ring- ing to the called line. A further path, the speech path, is set up by way of A7, B7, C7; and A8, B8, C8, and a bridge link BL. As soon as path continuity tests have been successfully conducted (described with reference to Fig. 18, not shown), the register connections to the calling line and ringing circuit are released. On reply, the ringing circuit to called line connection is released and the speech path by way of bridge BL remains. Should a fault be encountered the register presents its record of path identities for print out. The terminal to terminal connections are established one aftor the other, not concurrently. Since the calling and called line terminals are connected to two links the network must be such that paths can share the same switch in one or more but not all switching ranks; such an arrangement is described in Specification 113,234 (Application 34709/64). The switching network is of the "sectionalized" type described in Specifications 989,336 and 999,945. The network uses reed relay switches and the link circuits are of the various types described in Specification 1,041,757. The links may be in two groups to provide a choice of routing. The network is divided into two trains one of which caters for a high traffic concentration and the other for low traffic; this corresponds generally to one train for local traffic and another train for trunk traffic. Auxiliary equipment is connected in the trunk train. PBX groups are preferably served by A rank switches exclusive to such groups. The B and C rank switching sub-units each have a marker and an interrogator under the control of a common marker interrogator accumulator Switch path data elicited from the interrogators is analysed by route choice circuits which instruct the markers via the accumulators as to the path selected. Separate scanners are provided for the line circuits, for the registers, and for incoming junction circuits; the latter functioning as described in Specifications 1,020,381 and 1,063,991, to seize a register direct, the other scanners making demands of a common control coupler functioning with a program controller and a translator. Under control of a register and in conjunction with the translator a group search equipment governs selection of PBX lines, outgoing junctions, registers, ringing circuits and other auxiliary circuits. The program controller, described in broad terms with reference to Fig. 3, not shown, is said to employ digital processing techniques and to use a number of code-point translators in a modular construction of the sort described in Specification 1,083,666. The line scanner and register scanner cooperate with the common control coupler as shown in Fig. 4. As the registers are slow acting they are divided into four groups REG. Gp1 to REG. Gp4 each group served by a scanner RGS. Demands for service are presented to the common control from each scanner on highways AS1 to AS5 and are dealt with one at a time. When selected for attention a scanner is signalled and line or equipment identities are returned over arrays of gates CGL1 for the line scanner, and CGR1 to CGR4 for the register scanners. Buffer stores BS1 to BS4 are associated with the register groups to provide a path for data from the program controller and translator presented in common highway IS. If a register demands service the buffer store BS of its group is marked busy to the highway IS and the register identity is determined by the associated scanner RGS which halts on the demand presented over RA and returns this identity over RI so that only that register pursues its demand and other calling registers in the group are locked out. By way of RO and gates CGR the register now transfers the data it requires processing to the common control stores RCS when the common control selects the associated register scanner signalled as needing service over a highway AS1 to AS4. Registers are only connected to common control stores RCS during inter-digital pauses. If the register receives an impulse during connection but before data transfer, the connection is released and a fresh demand submitted at a later time. Data sent from common control over highway IS to a register is set up in all buffer stores BS together with the identity of the register concerned, the relevant register is the only one to respond to its own identity. When the processed data is returned to the register, the translator and program controller signals the common control access scanner to proceed in search of a fresh demand. When a register is seized for use in accordance with an identity provided by the group search equipment, the register identity is recorded in the buffer stores B5 so as to signal the scanner RGS over path SC. The scanner halts at the indicated identity which it reverts back over RI so as to activate the register required. The equipment number translator for local calls is shown in Fig. 5, and consists of units, of which only one is shown, giving a capacity of a thousand code elements. The thousands digit by way of a selector and sequence circuit selects the appropriate translator limit TX, which comprises a Dimond ring array, the hundreds groups of code wires at one end being selected by the tens digit and at the other end the tens groups being selected by the units and hundreds digits. The group search equipment is shown in Fig. 6, and comprises a translator which provides the identity of free lines or equipment in wanted groups and also provides translations such as may be required for party lines or changed numbers. Each group is subdivided into groups of ten and a sub-group counter GC, controlled by a logic circuit SL, steps over the sub-groups of a wanted group by successively marking inlets of a code point translator CPT which opens the corresponding gates IG to connect interrogating wires from the equipment or lines concerned to a selecting circuit SC. When a sub-group with a free member or members is encountered the circuit SC halts the search and selects the or a free member of the group, a Dimond ring translator TX producing the equipment number of the member so chosen. With double ended equipment having A and B terminals, such as registers and ringing circuits, only the A terminals are accessed by way of a group search. Connection to the B terminals must be a forced connection even though it employs the group search equipment. To this end the group search counter GC is set to the wanted sub-group and the selector SC to the wanted member of the group in order to compel the required equipment number as an output of translator TX. In this function the outputs of code-point translator CPT, which normally provide an input to the Dimond ring translator, continue to do so but do not control the interrogation gates IG. The group search may allocate a line or circuit which is otherwise busied before the use envisaged by the allocation matures. In such a situation the search is automatically renewed. The specification also discusses the necessary logical functions of the sub-unit marker interrogators, the route choice equipment, and the registers, in the context of the sectionalized exchange. Among the auxiliary circuits are coin-fee check circuits, multi-frequency signal receivers, and transfer circuits as described in Specification 1,056,304.