Patent GB-768093-A (GB)
Title: Automatic telephone system comprising electronic control equipments
IPC: H04Q3/00
Filed: 1954-04-15
Abstract: 768,093. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. April 15, 1954 [April 24, 1953], No. 11153/54. Class 40 (4). One hundred 10 X 10 cross-bar switches X1 ... X100, Fig. 1, serve 1000 lines AB1 &c. which have access to primary registers ER1 and to junction JS &c. through three switching stages X, Y, Z. An electronic marker MA selects links L1, L2 to interconnect a line with a register or a junction as necessary, equipment being marked by recurring series of pulses. When a call is made on line AB3, for example, the co-ordinates of the line are transmitted as recurring pulses to the marker MA which then hunts for a free primary register ER1. Having found a register, the marker selects free links, makes the connection, transmits the identity of the calling line to the register and releases. When the number of the wanted line has been dialled into the register, the marker is seized again. The numbers of the called line and the calling line are transmitted into the marker which then hunts for a junction and selects pairs of links before connecting the calling line. The second stage switches (with their associated links) are tested one switch at a time. If the call is local, a local junction JL is selected. This interconnects two switches. The called line is connected to the local junction before the calling line. Consecutive pulses each of 50 microsecs. duration are provided from a common source controlling ring circuits of flipflops which provide pulses in cycles of three different periods. The a pulses comprise 10 series of recurring pulses, a1 ... a10, Fig. 2, each series (e.g. a1) consisting of one pulse per cycle of 500 microsecs. (10 pulse widths). The band c pulses comprise respectively 13 and 11 series of pulses, b1 ... b13 and c1 ... c11, each series comprising one pulse per cycle of 650 or 550 microsecs. A combination of three pulses a, b, c is used to identify a line, a complete cycle of 3-pulse combinations taking 1430 pulses (71.5 millisecs.). Only the first 10 series of each a, band c cycle are necessary to identify 1000 lines, the remaining series being available to identify registers. When a combination identifies a line, the a pulse identifies the horizontal group of switches in the X stage, the b pulse identifies the vertical group of switches and the c pulse identifies a vertical bar in the switch to which the line is connected. The pulses of a series may be negative dropping from ground to - 50 volts and are then written as An, Bn or Cn (Fig. 3). Alternatively, they may be positive, rising from - 48 volts to ground (written an, bn or cn) or from - 200 volts to -180 volts (written an, #n, γn). Call detection, Figs. 4 to 9. When the loop is closed at Ab, the potential at 10 drops from ground to - 30 volts and diodes D1, D2, D3 conduct only at a coincidence of pulses (say Al, Bm, Cn) marking the line on terminals A, B, C. At a coincidence, triode DL transmits a positive pulse to three groups of ten tubes DA1 ... DA10, DB1 ... DB10, DC1 ... DC10. The grids of these tubes are marked by pulses a1 ... a10, b1 ... b10, c1 ... c10 and tubes DA1, DBm, DCn strike and register the identity of the calling line on relays RA1, RBm, RCn. A tube TA1 in the series TA1 ... TA10 repeats A1 pulses on lead fn to identify the horizontal group of X switches in a link selecting operation to be described later. The grids of discharge tubes DP and DE are marked with pulses Aj and bj (11#j #13) so that they strike in response only to pulses identifying a line and a register respectively. When DP strikes, relay. RDP operates and triode TP repeats B<SP>13</SP> pulses over lead ap to start selection of a free primary register at stage Z. A primary register is identified by a combination of an A pulse and a C pulse. In Fig. 6, register ER1 is connected later by operation of a vertical magnet VE1 and is identified by pulses on terminals Ae, Ce. The B13 pulses applied to diode de over lead ap open diode gate di5 so that at a coincidence of Ap, Cr pulses characterising a free register, say ER1, diodes di3, di4, di5 are all conductive and a negative pulse is transmitted to the grid of triode DJ. A positive pulse from the anode of DJ strikes one tube in each of the grips JA1-JA10, JC1 ... JC10 and registers the identity of the register on corresponding relays of the groups RJA1 ... RJA10, RJC1 ... RJC10. The Cr impulses characterise the switch Zr to which the register is connected and the impulses Ap characterize the outlet of the switch. One tube TCr of a group TC1 ... TC10 corresponding to the operated tube of JC1 ... JC10 repeats C pulses over one lead gr of a number g1 ... g10 to identify the switch Zr in the link selecting operation already referred to. Link selection. The links interconnecting two stages X and Y or Y and Z each comprise three wires a<SP>1</SP>j, blj, c<SP>1</SP>j or a<SP>1</SP>k, b<SP>1</SP>k, c<SP>1</SP>k. Lead gn bearing Cr pulses marking a switch Zr is multipled to all links connected to Zr. Similarly, a lead fn bearing Al pulses marking the horizontal level l of stage X in which the switch X1 serving line Ab is placed is multipled to wires cj in all links from level l. A link is marked free or busy by - 48 volts or ground on the C wire. Point 12 is reduced to - 48 volts only when both links are free and coincident A, B and C pulses are present on leads fn, gn and diode d10. The switches Y are characterized by By pulses on diodes d10. A positive pulse at the anode of triode DV identifies the links but only the By pulse position is registered by a gas discharge tube and a relay in the Groups TV1 ... TV10, RV1 ... RV10. The information registered at this stage identifies the calling line, the free register and the Y switch to be used to link them and is sufficient to enable control equipment CE, Fig. 9, to complete the connection in known manner, the C-wires being grounded to operate vertical magnets VEE, VL, VE1, the marker being released. The primary register - ER transmits dialling tone, the wanted number is dialled and the marker is seized again in a known manner not described. The register transfers its information to equipment TE (Fig. 9) in the marker, each relay shown being one of a group of ten. Relays PA, PB register the exchange digits and relays IG, ID, IU, the numerical digits of a called line. Relays IA, IB, IC register the co-ordinates l, m, n of the calling line. As soon as the information is registered, relay O<SP>1</SP>M operates momentarily to extinguish all conductive discharge tubes. In a call to another exchange, relays PA, PB enable a triode TR to repeat B pulses over leads ja and ap and thereby starts selection (by diodes di3, 4, 5) of a free junction in the group serving the called exchange. The junction code (A, C) is registered in the same manner as the primary register code and Cr pulses are transmitted over lead gn to identify the switch Zr to which the junction is connected. The Al pulses on lead fn marking the horizontal X group on which the calling line appears are now provided by TAl under the control of relay IAl after a delay in operating relay OM<SP>11</SP>. Links are selected as before and line Ab is connected to the trunk by the control equipment CE. In a local call, the register is connected as before and after dialling, triode JO and relay RJL operate in place of triode TR. A local junction is selected, its A, C code is registered on relays RJA1 ... RJA10, RJC1 ... RJC10 and the Z switch through which it has access to a called line is identified by C pulses on lead gn. The junction is connected to the called line first and to the calling line later. Relay RJL transfers the numerical digits of the called line from relays IG, ID, IU in equipment TE to relays EDC, EDD, EDU in equipment T<SP>1</SP>E. A circuit comprising contacts of relays EDD, EDC and a distribution frame Rp1 translates the hundreds and the tens digits of the called number into pulses indicating the X switch in which the wanted line appears. The units digit indicates the vertical bar within the switch without translation. Diodes dv, du, gate negative pulses identifying the wanted line to the grid of triode CL1. The grid of a triode CL2 is fed with pulses from each of the free lines through a diode tree in which diodes dj, dl, dn gate pulses characteristic of line Ab, when it is free, the line being marked on terminals A, B, C. If the wanted line is free, triodes CL1, CL2 are simultaneously pulsed and the positive pulse from the common anode resistor is registered on one of the tubes CA1 ... CA10 and an associated relay. The pulse also strikes tube CAL and operates relay AL to indicate that the called line is free. One of the tubes TA<SP>1</SP>1 ... TA<SP>1</SP>10 repeats A pulses over lead ap1 to lead fn to mark the horizontal level of the X switch in which the called line appears. Links are selected as before and the called line and the junction are connected under the control of CE, the tubes TC1 ... TC10 being extinguished. The connection of the called line is signalled by circuits CE, CS which operate relay RJM to start connector of the called line to the junction. The calling line X switch is marked on lead fn by one of the contacts ia1 ... ia10 and a TA tube. The Z switch through which the load junction has access to the calling line is marked by one of ten relays J, Fig. 9, one of the contacts j 1 ... j10 enabling a tube TC1 ... TC10 to feed C pulses to lead gn. The relays J are controlled by a circuit CDM which derives the necessary information from relays RJC1 ... RJC10 when the junction is selected. Links are selected as before and completion of the connection is signalled by relay FC which releases the marker. In an.incoming call, on junction JE, Fig. 6, the potential drops at jsa, the junction is identified by markings on terminals A, Bj, C applied to diodes di<SP>1</SP>3, di<SP>1</SP>4, di<SP>1</SP>6 (13 # j # 10) and the junction code (A,