Patent GB-331204-A (GB)
Title: Improvements in or relating to automatic telephone exchange systems
IPC: H04Q3/42
Filed: 1929-03-18
Abstract: 331,204. Standard Telephones & Cables, Ltd., (Hatton, W., Vriendt, C. de, and Rousseau, E. J.). March 18, 1929. Automatic exchange and metering systems.- In a telephone network, a calling line is automatically extended to a central point, and registering apparatus adapted to record the designation of the wanted office is taken into use at the originating office, the central point and the tandem office, if any. In the system described a network of 20,000 lines forming part of a network of 100,000 lines based on a main office M is formed by a " centre " office C, its satellites TD, D1 and satellites D2 of the offices TD. Any one of these 20,000 lines on calling is connected over two-way junctions to the " centre " office, where a register-controller RH of code translating type is taken into use. At the outgoing end of the junction or junctions used, discriminating and meter controlling apparatus MCC is picked up. The register controller and the apparatus MCC respond to the 1st 3 or, in certain cases 2 digits, and if necessary the " centre " office apparatus and/or that at TD is released. If the 1st 2 digits indicate that the call is to terminate in TD or in one of its satellites (other than the calling one) MCC at TID is released and a register controller R5 previously associated with the call, responds to the remaining digits and subsequently controls metering if the call originated in TD. The register controller R4 is described and claimed in Specification 331,222, and arrangements for setting up local calls form the subjectmatter of Specification 331,223. Methods of impulsing. In the system described the register controller, when ready to send, connects battery to the a-wire and a grounded relay to the b-wire. When the selector has become associated with its control circuit it puts battery on the b-wire to operate the relay in the register controller which then sends ordinary impulses. In a modified scheme, Fig. 16, forward loop impulsing is employed. The trunk is bridged bv a high resistance relay Hrr in series with a relay Sr. When the selector is ready Hrr is short circuited and Br in the register controller initiates the transmission of impulses. Extension of calling line D2 to " centre " office C. Line relay Lr, Fig. 2, starts the finders SDF, Fig. 3, of the links DLL. When the line is found. Ltr in the successful link energizes Ar which drives the selector S1 in search of a junction to the tandem satellite, <T>D. Jfr stops the selector and energizes Mcr which is followed bv Lbr and then Er in series with cut-off relay Cor.Lr, Ltr fall back. The test battery for energizing Jtr is derived from the upper contact of Lcr<1> through the incoming part (not shown) of the junction circuit. In the junction circuit, Fig. 4, Br<1> pulls up in series with Jtr and is followed by Dr<1>. Impulse relay Isr<1> bridges the outgoing side of the junction circuit and is followed by Lbr<1>, Ar<1>. At the other end of the junction, Jrt, Fig. 6, pulls up and starts the finders PF in the idle link circuits DLL, Fig. 7. Ar<2> in the successful one pulls up followed by Cr<2>, Br<2>. Dr<2> pulls up in series with the cut-off relay Cort and Sr<2> pulls up over the loop. Jrt, Ar fall back. On the operation of Dr<2>, PL hunts for an idle junction to the " centre office. Tr<2> pulls up when the junction is found and locks up in series with SC?.<2> which energizes Pr<2> which locks up. In the junction circuit which, except for the modifications indicated by the dotted lines and crosses is the same as that described above, Tcr<1> pulls up in series with Gr<2>, Fig. 7, which cuts off Sr<2> and extends the talking wires metallically to provide an impulsing circuit. At the other end of the junction, Jrc pulls up and the finders PL<5> of the idle links are started. In the successful one Ar
 pulls up followed by Cr<5>, Br<5>. Dr<5> pulls up in series with cut-off relay Jcrc, and Sr<5> pulls up over the loop. Jcrc releases Jrc, and Ar<5> falls. Association of registering apparatus with call. The operation of Ar<1> in the junction circuit Fig 4 at offices D2, TD, starts the switches SMF<3> of the idle discriminating apparatus MCC, Fig. 5, at these offices. In the successful apparatus Jtr<3> energizes Ar<3> which energizes Cr<1>, Fig. 4, Er<1> however remaining unenergized. The operation of Cr<2> in the link circuit TLL, Fig. 7, at office TD in a similar manner causes the association of a. register-controller R5, Fig. 8, by a switch PE. In the successful register-controller, Rtr4 pulls up and energizes Lr<4> which energizes Tcr<4>. At office C, the operation of Cr<5>, Dr<5> in the link, Figs. 9, 12, causes the association of an idle register-controller, Figs. 10, 11, by a switch PR. Rtr<6> in the register-controller stops the switch and locks up in series with Shr6 which energizes Tcr6 to send back dialling tone which, provided apparatus MCC is associated at both preceding offices, and the relays Cr<1> therefore are operated, is heard by the subscriber. Setting apparatus MCC at offices D2, TD. Isr<1> repeats dialled digits over the junction and over Lmr<3> to the registers SM1, SM2. Lmr<3> releases Cr<1> which short circuits CST<SP>1> to give a clean impulsing bridge for the. junction. At the end of the 1st digit. Cnra<3> pulls up to switch the impulsing circuit to SM2. When the latter goes off-normal a driving circuit is made for SMT which hunts under control of Ltr<3> for the e terminal marked by SM2. Ltr<3> (assuming the 2nd digit has ended) energizes Cnrb<3> which transfers the impulsing circuit to SMT. At the end of the 3rd digit, Cnrc<3> connects the impulse circuit to battery and arranges for Lmr<3> to send an impulse for the next two digits to the pairs Tra<3>, Trb<3>, Ura<3>, Urb<3> which are arranged like. the pairs of a counting chain. At the end of the final (5th) digit a circuit is thus made for Lcr<3>, which connects the jumpering points M1 - - M3 with relays Mra1, Mrb1, Dmr3. These points are jumpered to the banks a - - d of SMT. If the 2nd digit was even Etr<3> is energized to connect up wipers b, d, in place of wipers a. c. If the 1st digit was 6 or 7 indicating that the call is for the network based on the '' centre " office C a circuit is now made for Mra<1>, Mrb<1> or Dmr<3> which energizes Mra<1> and Mrb<1>. Direct earth placed on d by Lcr3 energizes Cr<1>, Er<1> in parallel. Jtr3 falls back and the circuit MCC is released. Discrimination. If the call is local to D2, Lcr<3> in the apparatus MCC there is operated as soon as the 3rd digit has been received and entergizes Lcr<1> in the junction circuit whereupon Jtr. Mcr in the link fall back since Jtr cannot hold in series with Br', and a local call is eatablished as described in Specification 331,223. If the call is to terminate in TD or one of its satsllites Cnrb<3> in the circuit MCC at TD after 2 digits connects ground over c (SM1) and one of the. wipers a - - d (SMT) to Lcr<3> which operates Lcr<1> to release Tr<3>, Scr<3>, Fig. 7. Qr<2> pulls up, locks in series with Q1r<2> and cuts off Gr<2>. PL then hunts for a local 1st selector under control of Tr<2> the test circuit being via the J-wi<p>er. which picks up the test potential, the c-wiper and the c-terminals of the local lines all of which are strapped together and connected via contact a of Btr<2>, to the test relay. When a selector is found, Scr<2> energizes Kr<2> and the local register controller is operatively associated with the link. If the call is to go via the " centre " office. Cnrc<3> when the 3rd digit has been received grounds wiper b (SMF3) over the circuit shown dotted, energizing Mra<1> which connects ground via the normal terminal of SMM and wiper (PL) Fig. 7 to short circuit Cr<3> and so release the local register controller R5. Hundreds selection in local call controlled by discriminator MCC. Mra<1> or Mrb<1> may be energized on the operation of Lcr<3> so that operation of Lcr<1> connects strong or weak ground over wiper d' to select a switch in the link circuit serving the wanted hundreds group. Operation of register controller R<5>, Fig. 8. The last 3 digits are repeated by Sr<2> to Str<4>, Tr<4> in series and the latter repeats them in succession to the registers SM100, SM10, SMU, the succession being looked after by relays Pr<4>, Sr<4>. When the 1st digit has been received, battery is connected over a (PE) to the a-wire to prepare the local selector, and when the latter sends back the " ready " signal, Br<4> energizes Fr<4> which cuts off Br<4>, starts the sending switch P and completes the out-impulsing loop including wiper Y. Each digit is stopped by J1r<4> and the transfer of control from one register to the next is done by relays Dr', Dir<4>. When the final digit has been sent, Rr<4> is operated, locks up, shortcircuits Cr' and releases Rtr<4> to release the register controller. l�t selector, Fig. 12. Battery applied to the a-wire of the link when the register controller is ready to send energizes the common relay Ar<7> which energizes Ecr<7> to drive the common control sn-itch SM<7> in search of the calling link. The switch is stopped by Pcr' which energizes J1r<7>, Fcr<7> in series. Bcr<7> is released by Fcr<7> and the switch therefore advances to its 11th terminals where Gcr<7> is energized and connects Br<7> to the b-wire to signal to the register-controller to begin sending. Br<7> afterwards holds over both wires in series and repeats to impulses from the register-controller over dialling relay 1r<7> to SM7. At the end of digit Gcr<7> is released, disconnects Br<7> and completes a driving circuit for the selector PJ which is stopped on an idle trunk or junction in the marked group by Hcr<7> which operates in a circuit over c (SM7), d (PJ), c (PJ) and locks in series with Scr<7> which energizes switching relay J2r'. The control circuit is thus released and restores itself to normal. " Direction switch " or incoming selector DS,