Patent GB-280665-A (GB)
Title: Improvements relating to automatic and semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1926-09-11
Abstract: 280,665. Siemens Bros. & Co., Ltd., and Grinsted, W. H. Sept. 11, 1926. Semi-automatic exchange systems.-In systems in which an operator at a manual position controls automatic switches at a distant office, the junctions have register senders associated with them ahead of the calls, such prepared junctions being indicated to the operators permanently (during busy times), or on depression of a key. The key strip controls the register by connecting strong or weak battery or ground or nothing to one talking wire and strong or weak ground to the other over contacts of the speaking key, depression of any key disconnecting the operator's set. The switches for associating the register senders with idle junctions may be of coordinate type and may be arranged to skip busy levels and to stop altogether when no junctions are available, but in the system described the switches are of co-ordinate type and hunt continuously over all their terminals. Preparing trunk. With the hunting switch, Fig. 3, and register sender, Fig. 4, in normal position, relay VR, energized over vertical springs k3, energizes the vertical magnet VM, and falls back when the springs k3 change over, energizing relay RR which locks up and re-energizes relay VR. The rotary magnet RM now operates in a self-interrupting circuit rm, rr2, vr3, gt3, 19. If there are no trunks available on the first level, relay PS pulls up over the C-wiper on its last terminal in series with relays SR(1), JT(1)(2). Relay SR does not pull up, but relay JT opens the rotary circuit, releases relays VR, RR and locks itself and relay PS(1). Relay PS is held also over PS(2), PT, w1, and relay PT releases relay JT which operates the rotary release magnet MM1. The restoration of springs w1 disconnects relay PT and holds relay PS momentarily over pt1. Relay PT falls sluggishly and releases magnet MM1 and relay PS. The latter before falling off re-energizes relay VR which delivers an impulse to the vertical magnet. On the relapse of relay VR, relay RR pulls up and re-energizes relay VR and hunting continues over the next level and so on. When the switch finds the last junction of the group busy, relay X pulls up instead of relay PS, and releases relays RR, VR, JT. Release magnet MM releases the switch, which then hunts over the first level again. When an idle junction is reached, relay ST pulls up in series with relay SA(1), (Fig. 2), which prepares the in and out circuits to the register sender and lights the multiple lamps LM belonging to this junction. Relay JT locks itself to the C-wiper over its low resistance winding 1 to mark the junction unavailable to the other switches and releases relays VR, RR. Relay SR now receives current over both windings but does not pull up. Registration of wanted number. During busy times the key LK is closed and the relays L, LC are operated with the result that the lamps LM of prepared junction glow continuously..At other times the operator closes a push OW to light these lamps. To guard against operators' seizing. a junction simultaneously, a tone current is fed to the sleeves of the junctions from the moment of seizure until the registration of the first digit over s3, c, 17, ca3, BS, and the operator tests with the tip of the plug in the usual way. When the plug is inserted, relay CS pulls up in series with relay S which puts out the multiple. lamps. The operator, with the speaking key SK thrown, writes down the number on the keyset KS. Depression of any key energizes relay R or relay P to connect ground directly or over a high resistance to the ring wire. At the same time the tip wire is connected over the key directly or over a high resistance to battery or ground or is left disconnected. On the insertion of the plug, relay S connects the grounded winding 2 of relay SA in place of its winding 1 to the wire c, whereupon relay SR is able to pull up over SR(2), 12, 11, jt2, C, SA(2), putting its winding 1 across jt2, releasing relays JT, RR, VR, connecting busy tone to the sleeve over sr6, 17, BS, and energizing relay D, Fig. 4, over 13, 24, a, p2, OT to ground in the headset. Relay D energizes relay E over 15. Relay E locks up, releases relay D4, extends wire a (connected to tip) to wiper 31 of the incontroller 1C and wire b, (connected to ring to relay J and wiper 32 in parallel, and energizes the incontroller magnet ICM over n3, e6 whereupon the switch takes a step removing a short circuit from a relay N which starts the interrupter motor, releases magnet ICM, locks itself and energizes the windings I of relays HE, TE, UE which lock up and remove a short-circuit over z<4> from a relay Z which opens the initial circuit of the relays HE, TE, UE. At each depression of a key, ground on the ring wire energizes relay J which energizes relay JA, and when the key is released these relays fall back in succession (relay JA sluggishly owing to a short-circuited winding) to send an impulse to the in-controller magnet ICM. If this ground is direct it also releases relay HE (TE or UE) over wiper 32 by energizing its opposing winding (2). The potential applied to the tip wire controls relays HA - - HD, TA - - TD, UA - - UD, thus ground or battery direct or over a high resistance energizes respectively relays HA, HO which lock up. If the connection is direct, relay HA energizes relay HB or relay HC energizes relay HD and these relays lock up also. If no connection is made to the tip wire the relays HA, HC buzz while the key is depressed but do not close any operative contacts. The setting of the relay groups determines the connection of different points in the bank of a counting switch SS over the relays CA(1), CB(1), CC(1) to the middle bank of the out-controller OC. Transmission by register sender. When the incontroller takes its second step, relay ST pulls up over 34, ST, 14, cuts the tone circuit and completes a circuit for relay A over a slow interrupter I'. Relay A impulses the magnet OCM of the out-controller OC which on its third terminals energizes relay C, which locks itself, cuts the above impulsing circuit, removes a short circuit from the impulsing contact a<1> which now sends impulses over d and the outgoing b-wire, and completes a circuit from a<2> over its winding 2 to magnet SSM of the counting switch SS which thus takes a step for each impulse sent over the junction. When the switch SS reaches the terminals marked by relays HA - - HE over relay CA(1), this relay locks up and disconnects winding 1 of relay C which holds momentarily over its winding 2 and contact a2, but at the end of the battery period short-circuits the impulsing contact and sends the counting switch home over quick interrupter I<2>, C<2>. The out-controller continues to advance under control of relay A until it reaches its second terminals, whereupon relay C pulls up to start the second digit which is terminated by the energization of relay CB. The out-controller is then moved round to its first terminals and a third digit is sent. On the relapse of relay CC, relay ST which has hitherto been held over 34 in successive positions and ca4, cb3, cc4 falls back and cuts off relay A which however holds until the end of the battery period c5. When the counting switch reaches home, the quick interrupter is extended over cc3, dr1, 42 to the out-controller magnet. Wiper 41 on its last terminal energizes relay DR which breaks this circuit and releases relay SR which releases the register relays HA - - HD &c. and relay E and completes a homing circuit for the out-controller over I<2>, 16, 18, 42, this circuit being extended when the out-controller reaches home to magnet ICM over the homing bank of the in- ,controller. Relay N is short-circuited in the normal position of wiper 34 and releases the register relays HE, UE &c. if necessary and relay Z which unlocks relays CA - - CC. Relay SA, Fig. 2, on the relapse of relay SR, switches the junction through. Correcting errors. If the operator withdraws the plug after registering a wrong digit, relays S, SR fall back and the register sender returns to normal. On the relapse of relay N the hunting switch tests the same junction and associates the register sender with it. Exchange attendants' supervisory arrangements. If a preselected junction is plugged up but no digits are registered, the relay ST is not operated and lamp AL glows, in series, if desired, with a delayed alarm relay. If fewer than three digits are recorded, relay ST falls back after they have been transmitted and the lamp AL lights again. This lamp flickers during the transmission of impulses. A disabling key K is provided on each hunting switch to enable the number of switches operating to be reduced at slack times. Statistical metering. A relay M, operated in series with the subscriber's meter when the key MK is thrown operates a statistical meter MR. This can be done after the subscribers have hung up since the key MK then connects battery over cs2 to the tip of the plug to re-energize the line relay and so connect up the meter. In the Provisional Specification the key set is connected to the cord over the ringing key, and circuits for the hunting switch differing slightly from those described above are described without reference to drawings.