Patent GB-190629647-A (GB)
Title: Improvements in Automatic Telephone Exchange Systems.
Inventor: MERK FRIEDRICH
Filed: 1906-12-29
Granted: 1908-03-02
Abstract: 29,647. Mark, F. Dec. 29. Telephone systems.-In a modified method of establishing connexions between subscribers on automatic exhange telephone systems, whereby the number of exchange switches is greatly reduced, the usual individual switches or first selectors for each subscriber are replaced by a number of so-called pre-selectors and first selectors, each of the Strowger type. common to a group of one hundred subscribers. Thus, in a system of 10,000 subscribers, divided into groups of one hundred, each group switchboard would contain ten preselectors, ten first and second selectors, and ten connectors, together with a group switch common to the whole group, and calling and cut-off relays for each subscriber. The lines of the hundred subscribers in each group are connected in multiple to the usual contact-banks of the pre-selectors, and when a subscriber calls, an idle pre-selector automatically connects itself to the calling line. The wipers of the pre-selector are permanently connected with a first selector, so that the calling subscriber is directly connected to a first selector and can make the desired connexion with the help of a second selector and connector in the usual way. The number of pre-selectors &c. corresponds to the probable maximum number of conversations at any time. The pre-selector and first selector thus constitute a pair of switches which resembles in its function the plug cords in ordinary manual exchange systems, in which one plug is connected to the calling subscriber and the other to the desired line. Each pre-selector is a switch of the Strowger type haviog the usual rotary, vertical, and release magnets D, H, M, Fig. 9, but no side switches are required, as connexion is permanently made with the first selector by the five wires a<o>, b<o>, 44, 45, 46. Fig. 4 shows the sub-station equipment of subscriber No. 1523, the usual impulse-sender n and ringing-key d being provided. The impulse-sender earths the a-line intermittently during the return of the dial, and following each return of the dial the b-line is grounded once. The contact u, when the dial is turned, breaks the connexion between the a and the b line during the return movement of the dial, but not also, as hitherto, when it it turned down. Fig. 6 shows the calling relays R, R" and the cut-off relays T', T" of the two subscribers 1523, 1538, who form part of the same group 1501-1600. The ten conductors 1, 2, 3 ... 10, Figs. 6 and 8, are connected to the contacts of the switch ZS at one end, and are connected together at the other end and by the wire 6<1> to the common calling relay R, Fig. 8. The contacts r<2> of the various calling relays R', R" are connected to the conductors 1, 2 ... 0 according to the "tens" digit of the subscriber's number, the contact r<2> of subscriber 1523 being connected to the conductor 2, and the contact r<2> of subscriber 1538 to the conductor 3, and so on. The group switch, Fig. 8, which comprises the four relays R, K, Z, E, the so-called tens-finder ZS, and the selector-finder WS, receives every call in the respective group, selects an idle pre-selector to be connected to the calling-line, and controls its connexion therewith. The selectorfinder WS is a rotating switch, the arm w of which moves over contacts leading to the pre selectors. When a subscriber calls, he is connected to that pre-selector on the line I, II of which the arm w rests at that moment. The arm w then immediately rotates until it comes to the line leading to the next idle pre selector. Fig. 7 shows the sources of current consisting of a large battery F, a small battery V, and a ringing or busy generator C. The interrupter U generates impulses of direct current, the function of which will appear later. Figs. 4, 6, 7 ... 12 are to be read in conjunction. Calling. If subscriber 1523 wishes to call subscriber 1538, he removes his receiver and proceeds to transmit 1, 5, 3, 8 current impulses successively in the usual way. Pre-selector. The removal of his receiver closes a circuit from the earthed battery F, Fig. 7, through the wire +, contact e', Fig. 8, wire 4<1>, calling relay R', contact t<1>, sub-station apparatus, contact t<2>, and wire 2<1> to ground. The relay R<1> completes the circuit of the common calling relay R, Fig. 8, through the contact r<2>, and wires 2, 6<1>, and this relay R in turn prepares the coupling-circuit of the pre-selector connected to the contact on which the arm w of the finder WS rests. This coupling is effected by the next impulse from the interrupter U, the current flowing from the interrupter through contacts k<1>, r, Fig. 8, arm w, wire I, lower contact of spring f<1>, and coupling-magnet G to the battery. The attraction of the lever g' completes a locking-circuit from the battery through the magnet G, contact g', wire 41, solenoid J<1>, common coupling-relay K, and contact e<1> to ground. The attraction of the levers g<2>, g<3> prepares the circuits through the vertical and rotary magnets H, D. As soon as the relay K is energized, the interrupter sends impulses through the contacts z, k<2>, Fig. 8, magnet J, wire 42, vertical magnet H, and lever g<2> to the battery. The preselector wipers are thus raised step by step until they are level with the contacts 21, 22 ... at which moment the arm i is connected to the conductor 2, which is connected over the contact r' and line 3<1> to the battery, so that the " tens " relay Z is energized and by moving over contact z cuts the magnets H, J out of circuit, at the same time inserting the rotary magnet D. This magnet receives impulses from the interrupter, and rotates the wipers of the pre-selector until they engage the contacts 23 of the calling line a', b<1>, c<1>, thus closing a circuit from V, Fig. 7, through the wire 7<1>, units or disconnecting relay E, wire 1<1>, contact r<1> of the calling relay, wire c<1>, and the wiper of the preselector to the battery V. The relay E opens the contact e<1>, thus de-energizing magnet G, solenoid J<1>, and relay K. The magnet G disconnects the pre-selector from the wires 41, 42, 43. The solenoid J<1> allows the arm into return to its zero position. The energizing of relay E also opens contact e' in the circuit of the calling relay R<1>, which is thus deenergized, the contact r<1> closing the circuit of the cut-off relay T' through the contact r', wire c<1>, and the pre-selector. It will now be seen that the calling subscriber is connected to the pre-selector and first selector, and is cut off from other calls by the re'ay T<1>. The group switch has also returned to position to receive a further call. After the first actuation of the vertical magnet H, the springs f<1>, f<2> rise to their upper contacts, the springy cutting off the relay G from the line I, so that the preselector shown in Fig. 9 cannot be coupled again until it returns to normal position. By the closing of the upper contact of the spring f<1>, the line I is connected to the interrupter, which sends a current impulse through the magnet W S whenever the arm w rests on the line I, thus causing the arm w to move on to the next contact. First selector. The first selector is connected by the wires a‹, b‹ and the wipers of the pre-selector with the calling subscriber's lines a', b<1>, and the relays A', B' are connected by the wires 44, 45, and the levers g<2>, g<3> with the battery F. The side switch e<1>, i<1>, o<1>, u<1>, controlled by the magnet S', can take up the usual three positions, the third position being shown in full lines. The single impulse corresponding to the "thousands" digit of the desired subscriber No. 1538, passes over the subscriber's a-line, pre-selector, wire a‹, lever e<1>, relay A', wire 45, aud lever g<2> to the battery. The relay A' controls the vertical magnet H<1>, which thus raises the wipers one step. The single rotary impulse coming over the subcriber's b-line energizes relay B<1>, thus actuating the magnet S' which moves the switch levers e', i<1>, o', u<1> to the middle position, thereby closing the circuit of the rotary magnet D' through the lever u<1> and interrupter U. The magnet D' rotates the switch until the wipers engage the contacts of an idle, and consequently unearthed, second selector ; this breaks the circuit through the magnet S' and allows the side-switch to move into its third position, disconnecting the rotary magnet and continuing the wires a‹, b<0> to the second selector. The test-lead c<1> is earthed through the lever o' and low-resistance releasemagnet M<1>, so that the second selector will test busy to other first selectors. The current through the magnet M' is not sufficient to energize it. Second selector. The selection of an idle connector proceeds in the same way as the selection of the second selector, the relay A', Fig. 11, responding to the impulses over the a-line to select the desired row, and the single rotary impulse over the b-line setting in action the rotary magnet D' to select an idle connector. In this case, the testlead c<II> is earthed through the lever o<2>, contact f<3>, (closed after the first vertical movement of the selector - wipers) and the low - resistance releasemagnet M<2>. Connector. The third set of impulses over the a-line energizes the relay A<3>, Fig. 12, causing the magnet H<3> to raise the wipers to the third row of contacts. The succeeding rotary impulses over the b-line allows the magnet S<3> to move the switch levers e<3>, i<3>, o<3>, u<3> to their middle position, disconnecting the magnet H<3> and substituting for it the rotary magnet D<3>, so that the fourth set of impulses turns the wipers on the contacts of the desired line. The succeeding rotary impulse over the b-line causes the relay B<3> to energize the magnet S<3>, and the armature s<4> of the latter closes a locking-circuit from the battery lead +, through the magnet S<3>, and armatures s<4>, a3 back to the battery, so that the switch-levers are not moved in