Patent GB-168611-A (GB)
Abstract: 168,611. Crowe, D. C. March 4, 1920. Automatic and semi-automatic exchange systems.-A cord terminating in a plug is driven along a branching tube to insert the plug in a selected jack. At each branching-point the cord has a choice of two paths, so that if there are n branching-stages connection can be made to any one of 2n jacks. In the apparatus shown in Fig. 5, there are six branching-stages A - - F, and a plug inserted in any one of the 64 holes at either end of the apparatus can be driven through to any one of the 64 holes at the other end, the path taken in any particular case being determined by the setting of directing-members at the six branching- stages. In the system of which the circuits are shown in Fig. 1, 50 holes at each end are fitted with jacks J, Fig. 13, connected to subscribers' lines, the other 14 holes being allotted to trunks connected to cords, Fig. 12. The subscribers' lines are represented in Fig. 1 by the line relays 0 - - 99 and the trunks by the wires TAL, TAR (representing answering trunks) and TCL, TCR (representing calling trunks). The cord circuits themselves are not shown in this figure, which only represents the circuits concerned in setting the directing-apparatus. Construction of switching-apparatus. At each branching - stags A - - F, Fig. 5, there are 32 directing-elements d, Fig. 8, each of which connects a pair of tubes c<1>, c<2> on one side with a pair of tubes c<3>, c<4> on the other side in such a way that for one position of the element d paths exist from c' to c<4> and from c<2> to c<3>, while when the element d is rotated to another position, paths exist from c<1> to c<3> and from c<2> to c<4>. All the directing-elements at a given switching stage are rotated together by a toothed wheel f, Fig. 7, which is rotated by a magnet M and pawl l. The wheel f engages toothed segments g, Fig. 10, which are fastened by spring clips i in grooves h of the elements d, studs d<1> on the clips i engaging a hole h<1>. To prepare a particular path for a given cord it is only necessary to energize the magnets M of a certain combination of the branching-stages. A magnet T, Fig. 6, individual to the cord, is then energized to engage a pinion t with a power roller w to drive the cord q through the tube o and along the prepared path. As soon as the plug enters the selected jack, a magnet W, Fig. 7, is de-energized, and by removing a detent n allows the wheel f to be restored, so that the apparatus can be used for setting up other connections. This is rendered possible by the method of mounting the toothed segments g on the elements d, a segment being able to rotate, even in the case of an element which is prevented from rotating by the fact that a cord is threaded through it, the studs i<1> in this case riding out of the holes h<1>. At the end of a conversation, a magnet U, Fig. 6, is energized to engage the pinion t with a reverse roller x to withdraw the cord. Instead of providing a separate clutch magnet for each cord, the clutches may be operated by cams on the searching- switches PL, QL and PR, QR, Fig. 1, by which the cord that is to be used is selected. Circuit operations; general method of energizing the proper combination of the magnets M of the branching-stages A - - F. It is obvious that for a given setting of the apparatus shown in Fig. 5, if a hole x at one end is in communication with a ho@e y at the other end any other hole x + n will be in communication with a hole y + n; that is to say, the setting necessary for effecting a given connection depends only on the numerical difference of the positions of the lefthand and hight-hand stations that are to be connected. The general method of selection is accordingly designed as follows. The left-hand station is arranged to impress its position number in code form on a series of relays AL - - FL, Fig. 1, by energizing a particular combination of these relays, and the right-hand station correspondingly impresses-its position number on relays AR - - FR. The two sets of code relays then jointly control a set of relays AD - - FD, energizing a combination of these relays that depends only on the difference of the two position numbers, and the relays AD - - FD energize the appropriate magnets of the series M (A - - F). The method of indicating the numbers by codes of the form .. - . - - (where a dash signifies energization of a relay and a dot non-energization) and of subtracting one code from another is explained in detail in the Specification. Method of energizing the code relays. Each line relay such as LR, Fig. 4, closes two circuits, one of which leads to one of eight terminals of relay C and the other to one of eight terminals of relay F. With the particular connections shown in Fig. 4, it will be seen that the first circuit causes the successive energization of relays B, A, X, and the second circuit causes the energization of relays F, D, Y, the relays A, B, D, Flocking themselves up. With different connections of the relay LR, other combinations of the relays A - - F would be energized. The relays X, Y, which are energized in all cases, serve to isolate the code relays and temporarily prevent them from being affected by the energization of another line relay. The method of wiring the line relays O - - 49 to terminals of the relays AL, DL and 50 - - 99 to terminals of AR, DR is shown in Fig. 1. Connecting a calling subscriber to an idle answering trunk. A calling subscriber on the right, say No. 83, is connected to the first idle answering trunk on the left, say TAL5, by the following operations. The line relay 83 energizes relay HR, which energizes relay KR, and circuits are closed through contacts ot the line relay to energize relays AR, BR, DR, FR, which represent the calling subscriber's code, and the isolating relays XR, YR, which prevent the code relays from being interfered with. Relay KR also energizes relay CL (the energization of which forms part of the code of all left-hand answering trunks) and relays XL, TAL, JL. Relay JL interrupts its own circuit by energizing relay SL and steps forward a searching switch QL , PL which tests the trunks TALI, TAL2, &c. At each step, relay JL closes a circuit through wiper PL and a front contact of relay TAL to energize a combination of the code relays DL, EL, FL corresponding to the tested trunk, but since the locking circuits of these relays are controlled by relay YL, which is not energized until an idle trunk is reached, the records of engaged trunks are not retained. When the relay JL next deenergizes after the idle answering trunk TAL5 has been reached (i.e. the first trunk having its test wire grounded), a circuit is closed through a back contact of relay TCL, wipers QL, PL and a front contact of relay TAL to energize relay YL, which locks itself up and locks and isolates the energized code relays of the series DL, EL, FL, so that the code of the trunk TAL5 is retained. In the present instance the code of the trunk TAL5 is recorded by the energization of relays CL, EL, FL. The code relays AR, BR, DR, FR and CL, EL, FL now jointly control the differential relays AD - - FD, energizing relays BD, DD, which represents the code of the numerical difference of the positions of the lines 83 and TAL5 on the two sides of the apparatus, and relays BD, DD energize magnets A, B, C and D of the series M to set the directing apparatus accordingly. The clutch magnet T, Fig. 12, of the cord TAL5 is picked out by a wiper L of the searching switch PL, QL. When either of the relays YR, YL is energized it closes a circuit for a slowrelease relay V, but when both relays YR, YL are energized, i.e. as soon as both the left and right codes have been recorded, this circuit is opened and after a moment the relay V de-energizes and completes the circuit of the clutch magnet. As soon as the plug enters the jack of the calling subscriber, his line relay LR1, Fig. 13, becomes de-energized, and the circuits shown in Fig. 1 are restored to normal. When the calling subscriber disconnects himself, relay H, Fig. 12, which was energized over his line relapses and de-energizes relay G, which closes a circuit for the restoring clutch magnet U, this circuit being opened at contact Z when the plug returns to its home position. The operations when a calling subscriber on the left is answered by a trunk on the right are similar, relays HL, KL, &c. coming into play instead of relays HK, HR, &c. and relays TAR, JR, &c. and searching-switch PR, QR, instead of relays TAL, JL, &c. and searching-switch PL, QL. Connecting a calling trunk to a wanted subscriber. In making a connection of this kind a temporarily-employed selector represented by the wipers a, b, Fig. 13, selects the wanted line and, if the line is idle, energizes its line relay LR1 in series with a relay S. The operations which follow are similar to those previously described, but relay S causes relay TCL or TCR to be energized so that the searcher hunts for the calling trunk instead of for an idle answering trunk. If the wanted line is busy there is no circuit over wiper a for relay M, and relays S, LR1 are not energized. Testing whether part of the required path is blocked by another cord. The circuits by which ground is connected to the trunk test wires extend through contacts of relays B (N, P, S, T), D (N, P, S, T), E (N, P, S, T), Fig. 1, controlled by the code relays, and also through contacts individual to the different tubular elements of a path and adapted to be opened by the presence of a cord in such element, the arrangement being such that if connection is required between a given subscriber and a given trunk, and if any element of the path necessary for this purpose is already blocked by another cord, the trunk test wire cannot he grounded and the switching apparatus is not set in action.