Patent GB-1001410-A (GB)
Title: Improvements relating to automatic telecommunication switching systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H04Q3/00
Filed: 1963-04-19
Abstract: 1,001,410. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. April 7, 1964 [April 19, 1963], No. 15549/63. Heading H4K. To prevent simultaneous testing of a wanted line by two marking control circuits, each of which is engaged with setting up a call across a network, the marking control circuits are made to rest in separate time intervals determined by the time a common translator is seized to service each call. Connections between line circuits LC are set up over cross-point stages SA, SB, SCL, by way of links XB, according to marks extended from decoding circuits DC1 to DC5. A number of registers REG are accessible to calling circuits over cross-point stage SCR. A route determining circuit RDC has a record of traffic conditions and, given requirements from the common translator Tx, can select a free route and seize an appropriate marking control circuit to establish the route. The translator Tx receives input from calling line identifier CLI and from the registers REG and is shared out by a scanner SC with associated gates Gg, Rd, Rg. A timing pulse source ST drives the scanner and also drives timing circuits in the marking control circuits; these timing circuits comprising a pair of bi-stable circuits PA, PB, which divide the pulse rate from ST by four, and a set of bi-stable circuits, C, B, A, T, U, V, W connected as a counting chain in that order and stepped by the quartered pulse rate. Connection of calling line to register.-The identity of the calling line from CLI is gated to the translator and a start signal R from CLI is sent to the route determining circuit RDC which plans a route between the calling subscriber and a free register REG and selects a suitable marking control circuit. The route is set up in the marking control circuit on sets of bi-stable circuits Bao, Bbo, Bco, Bci, and Bc, each of which provides an input to a respective decoder DC1 to DC5 at a time appropriate to the routine of connecting over the network. On seizure of a marking circuit the fact the connection is one to a register is indicated by the operation of bi-stable RG the output RG1 of which primes the input to bi-stable W and prepares AND gate G17 to mark the P and C wires of a connection to be made with the register. The fact that a calling side connection is involved is indicated by output SG of RDC, bi-stable H1 being operated to condition the circuit for service. The codes for decoders DC4, DC5 are gated direct and by operation of relay CCR connect a free register to the marking control circuit. The connection shown in the drawings, Fig. 3, is to a link circuit XB by means of relay CCL, but the connection with the register will be similarly made over L, P, H, and C wires. The first pulse on lead Pu from the divide-by-four pair PA, PB, operates W and C to relieve decoder DC3 of inhibitions and by operating relays such as RCL and RCR to make a path to the register over stages SCL and SCR. The next pulse on lead Pu operates B, and the next operates A, successively to operate relays such as RB and RA to connect over stages SB and SA. A further pulse on Pu operates T and on lead Ti this primes test bi-stable P which responds to the P wire from the register and over gates G13 and G13<SP>1</SP> reverts earth and negative battery on the P and C wires to enable the register to hold the connection to the calling subscriber. In the counting chain C, B, A, T, U, V, W, the bistable C restores when A responds, B restores when T responds, and so on. When the count reaches V, gate G6 opens to. restore H and release the marking circuit. Connection of calling and called lines.- Acquainted with call data the register communicates through the translator with the route determining circuit RDC which in accordance with its plan for the call seizes a marking control circuit for the calling side connection and another for the called side connection. To enable a second attempt at finding a free p.b.x. line to be made the called marker control circuit establishes its connection first. In the called marker control circuit a signal SD from RDC operates H1 to put the circuit in service and also operates CC to indicate a called line connection. Decoders DC4, DC5, operate a relay, such as CCL, to connect a link such as XB. The link is symmetrical and can be accessed from either side. With CC operated, W operates to the first Pu pulse with C and connection to the calling line is established with successive steps from the decoders DC3, DC2 and DC1, in the same manner as with the connection to the register on the calling side. The relays RA, RB, RCL are held by positive battery on the H-wire from the marking control circuit. With CC operated test bi-stable P is primed and the fourth Pu pulse operates T enabling bi-stable P to examine the condition of the P-wire. If the called line is free P operates and by opening gate G11 allows F to operate to the negative L-wire. Gates G13, G13<SP>1</SP> now revert earth and battery to the link to condition it to hold the connection. When the count of Pu pulses reaches V with T restored, gate G6 opens to restore H and release the control circuit. Should the test find busy conditions either by way of the P-wire, or if a line is in process of connection to a register by way of the L-wire, then F does not respond and when the Pu count reaches U and V gate G14 opens to put positive battery on the C-wire so as to condition the line to send busy tone. With T restored the control circuit releases. Connection by the calling side marking control circuit is similar, H responds to signal SG, but with the response of neither CC nor RG the count of Pu pulses does not start with W already operated. The count therefore proceeds from C to W without effect and is then repeated with W operated to effect the connection, as before, by successive operation of the decoders. Class of service.-This is indicated by the translator in response to the calling line identity. Specification 999,945 is referred to.