Patent GB-171433-A (GB)
Abstract: 171,433. Siemens Bros. & Co., Ltd., and Christian, D. A. July 12, 1920. Automatic and semi-automatic exchange systems.-A special trunking and testing connector a<1>, b<1>, c<1>, Fig. 2, can be seized either by a trunk operator's selectors a - - f, Fig. 1, or by a test clerk's selectors a - - f, Fig. 2, these selectors being two-coordinate switches which have no hunting-movement and are set by impulses representing the first two digits of the wanted number. The connector is tested by the trunk'selecfor, Fig. 1, and by the test selector, Fig. 2, over separate circuits, and, if tested by the former while engaged by the latter, is automatically released and taken into use for the trunk call. The connector a<1>, b<1>, c<1> is provided with vertical, rotary and release magnets H<1>, D<1>, M<1> but has no individual control relays, being controlled entirely by relays at the preceding selector. Establishing a trunk connection. The relay A, Fig. 1, energized in the b lead over the operator's impulse sender, energizes relay N, which locks itself in the sleeve circuit and energizes relay E in a circuit n2, z6, E, a1, f1. At the first interruption in the impulse circuit, contact a1 opens a short-circuit round relay F, which becomes energized in series with relay E, and at the termination of the impulse; and of each succeeding impulse, vertical magnet H is energized in a circuit s2, e2, f2, a3. Between impulses, relay E is short-circuited over contacts f1, a1, and at the termination of the impulses relay E slug-' gishly de-energizes. At the first interruption of the second series, relay G, being now no longer. short-circuited either at contact e1 or at contact a1, becomes energized in series with relay F in a circuit e1, f1, z6, n2, and at the termination of the impulse, and of each succeeding impulse, rotary magnet D is energized in a circuit s3, g2, f2, a3. Between impulses relay F is short-circuited over contacts a2, g1, and at the termination of the impulses relay F de-energizes, removing the short-circuit from relay E and closing a shortcircuit round relay G, which also de-energizes. In the interval between the de-energization of relays F, G, both windings of test relay P are connected to wiper c in a circuit f3, g3, n3, and on the de-energization of relay G, relay S is energized in a circuit K3, z4, g3, f3 and locks itself up. If the connector a1, b1, c1 is idle, or is in use by a test clerk, relay P becomes energized over resistance w, Fig. 2, and locks itself to wiper c through its low-resistance right-hand winding. If the connector is in use by a test clerk, then before relay S has had time to become energized the low-resistance left-hand winding of relay Z is connected to wiper d in a circuit f4, s5, p3, and is energized in series with magnet M<1>, Fig. 2, which releases the connector. Contact K2<SP>1> is then opened, releasing relay Z, which permits relay S to become energized. If the connector is in use by another trunk operator, the potential on wiper c is insufficient to energize relay P, and a tone and flash circuit 107 is connected to the operator's cord in a circuit p2, s4, relay A at the same time being disconnected. Assuming that the connector is idle, or has been released from its test function, the third and fourth sets of impulses control relays A, E, F, G as before, but are now repeated over contacts s2, s3 and wipers e, f to the vertical and rotary magnets H<1>, D<1> of the connector, which is thus set to the wanted line. After the fourth set of impulses, the de-energization of relay F completes at f<4> a circuit through both windings of relay Z, wiper d and magnet M<1>, which however is not energized owing to the high resistance of the circuit. Relay Z disconnects relays A, E and completes the through talking circuit. After conversation, when the operator takes down her cord, the relapse of relay N closes a circuit n2, z5 through the low resistance winding of relay Z to energize the release magnet M'. The opening, of contact K2<SP>1> then deenergizes relay Z, which closes a circuit n2, z5, K2 to energize the release magnet M. Operation by test clerk. The test clerk plugs into jack 20, Fig. 2, and throws a key 40 to connect his impulse sender to relay A, which energizes relay N, which locks itself in the sleeve circuit. The selector is then set to the terminals of the connector a<1>, b<1>, c<1> under control of relays A, E, F, G in a manner similar to that described in the preceding paragraph. In the interval between the de-energization of relays F, G, after the second set of impulses, ground is momentarily connected in a circuit f3, g3, z4, n3 to wiper c and contact K<1>1, and the left hand winding of relay Q is momentarily connected in a circuit n4, f4, s4 to a junction point 31, 30, to which all the relays Q and all the normal contacts K1<SP>1> are multipled, so that if the connector is idle, the normal contact K1<SP>1> being closed, relay Q is energized, locks itself in a circuit q1, n4, and lights a tell-tale lamp 70 before the test clerk. A moment later, on the de-energization of relay G, relay S is energized and locks itself up, transferring the impulse circuits from the selector magnets H, D to the connector magnets H<1>, D<1>, so that the third and fourth series of impulses set the connector on the line to be tested. On the de-energization of relay F, after the fourth set of impulses, a circuit n4, f4, s4, q4 is closed through both windings of relay Z over wiper d and magnet m<1>. Relay Z becomes energized, disconnecting relays E, F, G and completing the through test circuits, but its high resistance prevents the energization of magnet M<1>. The test wire of the selected line is now connected through c<1>, K1<SP>1>, c, n3, z4 to a point in the circuit w1, w2 of such potential that the line, if previously idle, is marked busy, and if previously busy is not released. By opening key 50, the test relay of the selected line can be de-energized, to enable the test clerk to test the automatic equipment over the preliminary selector of the line. For routine testing, the connector can be stepped from one line to the next by energizing the rotary magnet D<1> by a key 60. Release takes place, when the test clerk takes down his cord, in the way described in the preceding paragraph.