Patent GB-596752-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/58
Filed: 1945-08-02
Abstract: 596,752. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and LONG, D. P. Aug. 2, 1945, No. 19890. [Class 40 (iv)] A single-motion selector at a satellite exchange has outlets to main exchange junctions, one of which is automatically seized when the selector is taken into use, and to other junctions and local selectors, its contact bank being divided into sections with all the outlets of any one group connected in one section, and discriminatiiig and control apparatus is associated with the selector so that the receipt of a discriminating digit indicating a call other than one via the main exchange also determines the section of the bank in which search is to be made and, if necessary, brings about a preliminary movement of the wipers to a position adjacent to that section. As shown, a motor-driven uniselector has its bank divided into two parts, each of two sections, the parts being associated with the odd and even-numbered wipers respectively and the sections designated W, X, Y, and Z. Four pairs of wipers are provided for each section, two for the speaking wires, and one each for the testing and marking circuits. Each section comprises 52 contacts, a pair of sections Wand X, or Y and Z being wiped in succession. The first contacts in the N and Y arcs are normal contacts and are unconnected to outlets but in the Y speaking and test arcs they are connected to a circuit for holding the selector under permanent loop conditions. The 52nd contacts in each arc are '' lost " contacts on which the selector is stopped under busy conditions. Junctions to the main exchange appear at the beginning of the W-section, the contact following the last junction in the W test arc being connected to the " last " contact as indicated at jlc. Seizure of selector. This may take place only when the control circuit with which the selector, in common with seven others, is associated is free, as denoted by battery on the p wire over wipers ma2, mb2, and mc3, all normal, and a contact of relay BA. On seizure A, B and BA pull up, followed by K, which couples the selector to the control circuit, and C, which holds B in series with the first marking switch magnet MAM. The selector hunts for a free main exchange junction, T and TA pulling up when one is found to stop the selector and switch through the calling line to the main exchange, where dialling tone is applied. Relay A is held locally by AX which is included in the loop, and T is shortcircuited by earth over the p wire from the junction relay set. Impulses are transmitted by the caller over the junction and AX repeats them via A to set the first marking switch, B and C holding during impulsing. At the end of the first impulse train A, AX and B hold and the release of C operates M (if G has not been operated), which substitutes MBM for MAM for the reception of the second digit and re-operates C. The release of C also extends earth to wiper ma4 for the operation of the appropriate discriminating relay G, GX, L, PA or PP, if any. On the release of C after the second train, the operation of N connects up the third marking switch. After the digit which determines whether the call is to be completed over the main exchange junction or not has been received, either G or L becomes operated. Calls to main exchange. Discrimination may take place on any of the first three digits. If it is to be on the first, the relevant contact of arc ma4 is wired to terminal g, and that of the marking arc ma3 is unwired, main exchange junctions being marked over terminal gp1 independently of the marking arcs. For discrimination on the second digit, the connection to terminal g is made over ma4 and mb5 or 6 in tandem, and similarly for third digit discrimination the tandem connection includes also mc 5 or 6. Corresponding connections are extended from ma3. The subsequent operation of G brings up L (ineffective in this instance), and H which switches through the connection independently of AX, which by its release initiates the release of the control circuit. Local calls-outlet in W section. The contact in the discriminating arcs to which connection is made after reception of the discriminating digit is strapped to terminal l, so that L operates, and connects wiper ma3 in place of the junction marking wire gp1, while TA falls away and releases the junction, and is followed by AX, subsequent digits being received by A. On reception of the digit determining the outlet group, earth is extended on the release of C to terminal g, G operates and the selector hunts for a free outlet marked over the marking arcs and wires gp2 to gp6. On finding, T and TA pull up, followed by H, which switches through and initiates release of the control circuit. If the discriminating digit is also to determine the outlet group, connection is made to lg instead of l, so that L and G come up at once. Outlet in Y-section. The discriminating digit brings about the marking of terminal pp over the normal contact of a subsequent discriminating arc, and on the release of C, PP comes up, operates L, disconnects the " last " contacts in the test arcs, releases the junction, marks the normal contacts in the W and Y sections of the marking arcs, releases TA and starts the selector which drives to its normal position where PP is released. The discriminating arc contact is connected to gx to which connection is made after reception of the digit determining the outlet group so that G and GX operate in series, the latter relay bringing up WS to connect up the even numbered wipers. Relays T, TA and H operate to a free outlet, the connection is switched through and the control circuit is released as before. If the discriminating digit is also to determine the outlet group, GX is provided with a second winding to which the marking on pp is transferred bv a make-before-break contact of L so that GX and G pull up at once. Outlet in X or Z sections. Terminal pa is marked in place of pp, PP and L come up as before and PA marks the first contact in the X section of the test bank, to which the selector is driven. The extension of earth to g or gx, after reception of the digit denoting the outlet group, depending on whether the group is in the X or Z section, operates G or G and GX as the case may be. Dialling of unallotted numbers. All contacts in the discriminating arcs not used in the determination of the destination of a call are strapped to terminal s, so that when connection is made to one of these by a discriminating wiper S and L pull up in series and TA falls away releasing the junction and relay AX ; any further impulses are rendered ineffective by the disconnection of relay C, and NU tone is transmitted over the lower winding of relay A to the calling party. Busy conditions. If no free junction to the main exchange is available the selector drives to the contact following the last junction where T pulls up to stop the selector, and LC operates connecting up dialling tone and operating an overflow meter. If the digits dialled denote a local call, its connection proceeds normally, LC being subsequently released by L or PP, but otherwise the operation of G substitutes busy tone. Congestion in a local group of outlets results in LC being operated when the selector reaches the " last " contact, and G being up, busy tone is reverted and the appropriate overflow meter is operated over the marking switch wipers, Fig. 3. Release of control circuit under permanent loop conditions. The operation of relay C on seizure of the selector connects the normal contact in the ma7 arc to an " S pulse " wire which is earthed periodically. Relay S operates to the first of these pulses and locks up. After a predetermined interval an earth pulse is applied to the " Z pulse " wire and if no impulse has been received L pulls up, disconnects the magnet MU and relay C, and releases TA to release the junction. The release of C brings up G and the selector drives to the normal contact of the W section, marked over ma3 normal, whereupon T and TA pull up, followed by WS and H. The calling line is now switched through to WS, which holds as long as the loop persists and maintains H, the control circuit being released and an alarm being operated over wire pg, Fig. 1. Outlets common to two digital values. Differentiation between the two digital values which select such an outlet is effected subsequently by a signal transmitted forward before the relapse of TA. With G and TA up earth over wiper mc2 is extended, if the digit is even, to the positive wire to effect the differentiation at the next switching stage in the manner disclosed in Specification 378,585.