Patent GB-1197448-A (GB)
Title: Improvements in or relating to Automatic Telephone Exchanges
Inventor: ARNOLD JOHN SPENCER
IPC: H04Q3/54
Filed: 1966-12-29
Abstract: 1,197,448. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. 29 Dec., 1967 [29 Dec., 1966], No. 58214/66. Heading H4K. In a sectionalized exchange of the type in which a connection involves a path through a subsection in one plane of subsections and a further path through a subsection in one of the adjacent planes of subsections, the inlets to the first rank (i.e. the C) switches in the two planes are cross-connected via link circuits and D rank switches, the latter switches being controlled by one only of the two markers pertaining to the two subsections involved in the connection. In a previous system of this general type the D switches were located on both sides of the link circuits and were operated by a centralized control circuit. Network (Fig. 1).-This comprises four switching units U1-U4 each consisting of A, B and C ranks of reed relay matrix switches. Subscribers lines, registers, trunks &c. are connected to the outlets of the A switches AA whilst link circuits LU are connected to some of the inlets of the C switches (the connections to the remaining C switch inlets are discussed below). The B and C switches in each unit are divided into four subunits i.e. SUIW-SUIZ for unit U1 whereby corresponding subunits in each unit make up the planes W, X, Y, Z. There is full availability between the (96) inlets of the subunits C switches and the 1000 or more outlets of the A switches pertaining to the unit containing this subunit. In subunits of planes W and Y, the C switches inlets are connected to individual link circuits LU which in turn are connected to the inlets of individual D switches having 4 outlets each. The latter outlets are connected to a C switch inlet in each of the subunits of one or the other of the adjacent planes. (In practice the D switches are 4 x 4 reed relay crosspoint matrices having one inlet per corresponding inlet of the four C switches in a plane). Connections through the BC switches are controlled by individual subunit markers which are supplied with data from a centralized marker and route finding arrangement MCU, RCE. The "control" markers associated with W and Y plane subunits, "know" the type of link circuit required and the identity of the adjacent plane X or Z which will be involved in the contemplated connection in addition to the data regarding the selected path through the BC switches of their subunits whereas the X and Z plane "slave" markers are only aware of the path data pertaining to their associated subunits. A switches (Fig. 2).-In the general case these are built up of thirty 4 x 4 reed relay matrices of which the diagonal D1 and split diagonals D2, D3 represent one 120 x 40 A switch (in practice, the three diagonals are constructed as three separate switch blocks but the indicated schematic leads to simplification of the trunking diagram). Each matrix has four outlets (horizontals 1, 2, 3, 4) which are connected to peripheral equipments such as line circuits and four inlets (verticals) which are connected either to the inlets of two other matrices in the same column or to the inlets of two other matrices in the same row, see for example inlet Z connected to the first vertical in the three matrices in the leftmost column and inlet W10 connected to the last vertical in the three matrices in the bottommost row. Each A switch outlet thus has access to one outlet from each of its unit's subunits in planes W, X, Y and Z while each of these subunits has 10 outlets per A switch. With the general A switch shown a concentration of 3: 1 is obtained for the subscriber lines but other concentrations can be obtained by altering the number of diagonals that form an A switch or by using 2 x 4 switches. B, C switching subunits (Fig. 3, not shown) consist of eighteen B, 8 x 10 reed relay matrices and eight C, 12 x 18 reed relay matrices which provide full availabilty between 96 C switch inlets and 180 B switch outlets. D switches Figs. 4, 5.-As previously indicated, in each subunit there are 96, 1 x 4 D switches connected to the 96 inlets of the C switches. In order to conform to the standard 4 x 4 switching module, the outlets from correspondingly numbered D switches in each subunit in a plane i.e. outlets 01-04 for switches D1 in units U1-U4 of plane W, are multiplied so that only 96, 4 x 4 D switches are required per plane. In each plane W and Y the multipled outlets of the first 48 D switches are connected to the 48 multipled inlets 49-96 of the C switches in the preceding plane i.e. Z and X while the second set of 48 D switches i.e. those numbered 49-96 are connected to the 48 multipled inlets 1-48 of the C switches in the following plane i.e. X and Z. By these means each subunit has access to every other subunit in the preceding and following planes. In order to allow for expansion of the exchange up to say 20 units, the D switches are preferably made up from a horizontally and vertically multipled 5 x 5 array of 4 x 4 modules with the unused inlets and outlets being initially unconnected. As an alternative it is suggested that the link units and D switches may be provided in respect of half the C switch inlets in each subsection of every plane rather than in respect of all the C switches in the subsections of alternate planes. In this case however all the markers would have to have the same facilities as are provided only in the presently described control markers. Operation, Fig. 6.-In order to connect two peripheral equipments EA and EB, the route choice and central control equipment supplies the control and slave markers M(c) and M(s) respectively in the selected subunits of adjacent planes with the identities of the selected A, B and C switch outlets. It also supplies to M(c) only the identity of the C switch inlet i.e. the link circuit which is to be used, and the mode data viz which of EA and EB is the calling party. Assuming that EA is the called party, the control marker M(c) closes the C-inlet identifying contact CISI and that one of the 18 MC(c) contacts corresponding to the selected outlet level from the C switches. Consequently an individual C switch reed crosspoint C(c) is energized and since contact MB(c) corresponding to the preselected B switch outlet level is also closed, the required B switch crosspoint B(c) is partly energized to prevent problems of back emf occurring when MC(c) is opened. When the latter is opened, B(c) energizes fully and at the same time contact MA(c) corresponding to the particular A switch outlet in a particular A switch diagonal is closed. In fact there will be 10 corresponding outlets in an A diagonal marked by closure of MA(c) but with the marking extended forward by the operation of B(c) only one A switch crosspoint A(c) will energize fully when MB(c) is opened. Depending on the result of the busy or free test performed by BTE(c) which is connected via contacts C1S4, 5 to the -<SP>ve</SP> and P wires of the now completed path between EA and LU either, H1 and H2, or, H2 only, will be actuated in the link. The former actuation (H1 and H2) ensures that the calling and called side paths are held and ringing current and tone sent while the latter actuation (H2 only) ensures that the calling side is held and busy tone reverted. With the calling side complete (irrespective of whether it is free or busy) M(c) closes its "other side unit" contact OSU whereby that D(c) relay which provides access between LU and the preselected subunit handling the calling side is operated. Shortly afterwards the slave marker M(s) closes its contacts MC(s), MB(s) and MA(s) in that order to cause the relevant C(s), B(s) and A(s) crosspoints to be energized successively. The operation of relay RS, which comes up with C(s) when OSU opens, controls the operation of a sequence switch which governs the actuation of contacts MC(s), MB(s) and MA(s). The calling side (and the called side if it is free) is then held from earth in the peripheral equipment to - 50V in the link LU while the markers are released. If the calling side had been represented by EA, then control marker MC(c) would have caused slave marker M(s) to set up its path first, the necessary operations being otherwise similar to the above.