Patent GB-586380-A (GB)
Title: Improvements in telephone systems
IPC: H04Q3/00
Filed: 1944-12-08
Abstract: 586,380. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., TAYLOR, R., and BAKER, G. T. Dec. 8, 1944, No. 24550. [Class 40 (iv)] In an arrangement for working between an exchange employing step-by-step switches and an exchange employing revertively-controlled power-driven rotary switches, a converting unit including a rotary stepping switch is permanently associated with each one-way junction. On calls from the step-by-step exchange, the switch is advanced alternately by dialled digits and by trains of revertive impulses from the rotary exchange. On calls from the rotary exchange, the switch by its movement sends alternately trains of revertive impulses to the register-controller and trains of forward impulses to the step-by-step exchange. Step-by-step to rotary. The converter. Fig. 3A, is associated with a repeater, Figs. 1, 2, which includes an impulse generator of the kind described in Specification 458,095 and is such that it can be readily modified to act as a straightforward repeater if the network becomes completely converted to step-by-step operation. Relay JAR energizes immediately the repeater is seized and over wire 18W initiates retransmission from the regenerator, impulses being sent to the switch CS at springs IMP2 and the impulse springs IMP1 in the outgoing loop being ineffective. Relay JAR falls back and relay IZR energizes over wire IZW when the stepped pin RSP on the sending arm engages the first displaced pin CDP and connects up CFR which completes the fundamental circuit over the junction and places the switch CS under the control of relay OSR. Relay OTR energizes if the first digit is odd. The switch CS is now stepped by revertive impulses to position 11 or 12 according to the condition of OTR, whereupon FTCR pulls up, opens the fundamental circuit and advances CS to position 13. Relay JAR re-operates, and similar actions take place for the second digit. The first rotary selector effects brush tripping on one of five levels in response to the first digit, and the discrimination between odd and even digits is passed on to the next stage, consequently the switch CS stops in position 23, 24 or 25 dependent on OTR and on OHR which operates if the second digit is odd. As regards the units digit, the operation of the odd tens relay connects up FTCR ten steps ahead of the position to which it is directly connected. Finally, the switch CS reaches a position in which switching relay ESR operates. Rotary to step-by-step. The converter, Figs. 4, 5, is employed in the case where a rotary exchange is extended by the provision of additional step-by-step equipment. When taken into use by a rotary selector, relay CO energizes over the test wire, seizes the step-by-step selector over the + wire and closes the fundamental circuit through relay GL. Relay AR operates when earth is returned on the P wire and completes a loop to the selector. The switch C advances under the control of stepping relay PR which at each operation sends a revertive impulse by earthing the a wire until the register is counted out, when GL falls back. The switch C continues, howover, and impulses are now sent foward until position 12 is reached in which GL re-operates locally and AR falls back, connecting battery to the a wire to bring in the next register. The fundamental circuit is remade in position 16, and the second digit takes effect in a similar manner. As regards the units digit, any number up to 20 revertive impulses may be required. If the number is 10 or less, GL is back when the switch C reaches position 39, AR does not re-operate, and GL comes up in position 40 to end the forward impulses, which are sent over the + wire. If the number is greater than 10, however, AR re-operates in position 39 and remakes the loop, thereby energizing a wiper-switching relay temporarily connected in the - wire. In position 50, GL re-operates to end the forward impulses, and CO is disconnected. In the case of a separate step-by-step exchange, relay AR is arranged to operate when the switch C moves off-normal. Incoming traffic from the rotary exchange is conveniently dealt with by the provision of a separate group of penultimate selectors with the levels arranged on rotary principles, the 200-point final selectors being common.to all traffic. Routing. The invention has particular application to the Wellington and Hutt Valley areas of New Zealand which if ultimately fully converted to step-by-step working would form a 5-digit closed system. In order to provide for subsequent development, particularly in the Hutt Valley area, route controllers may be provided at certain exchanges. The route controller, Figs. 12, 13, is seized from the first selector and the dialled digits are stored on an impulse regenerator. In addition, the first or the first two digits, depending on the trunking requirements, are recorded on a switch D and bring about the operation of a relay such as ADR, BDR. Relay OH now energizes and the switch continues to step by self-interruption, the later contacts being marked over cross-connections to control the sending of one or two routing digits or none at all. If no routing digits are required, relay OH is maintained in positions 21, 32 over the NIL terminals and the switch continues to position 45. If two routing digits are required, OH falls back in position 21 and connects up IG, whereupon impulses are sent out at springs IMP2 while the switch is stepped over springs IMP1 until a fresh circuit is made for OH over the marked terminal in the first group. Relay OH again falls back in position 32 and the second routing digit is sent in the same way. Relay SO pulls up in position 45 and starts sending from the regenerator, the switch D being advanced one step for each digit. One or more digits, however, may be absorbed since the impulse springs IMP are normally shunted by relay SD which is controlled over cross-connections by the switch D. Finally, relay CO operates in position 50 and releases the route controller. Figs. 14, 15 show a layout of the Hutt Valley area illustrating the use of route controllers. For calls from Lower Hutt to the Wellington area, any first digit except 6 or 8 gives rise to a routing digit 7 or 8 according as the wanted exchange is rotary or step-by-step. In the former case, all the dialled digits are sent, but in the latter case, if there is only one step-by-step exchange in the Wellington area, the first dialled digit may be absorbed, as first selectors at Central are unnecessary. For local calls, no routing digit is required and the first dialled digit is absorbed. For calls to Upper Hutt, the routing digit is 9 and the first digit is absorbed, while for calls to Eastbourne, which comprises only 800 lines, the routing digit is 4 and the first two digits are absorbed. It should be noted that on calls from Eastbourne two dialled digits may be necessary to determine the destination. Certain junctions may be accessible over either of two levels, the low grade ones being first choice in one level and the high grade ones first choice in the other level so that the latter may be more readily available for the longer connections. A layout of the Wellington area is also given, Figs. 8-10 (not shown).