Patent GB-257661-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-06-04
Abstract: 257,661. Automatic Telephone Manufacturing Co., Ltd., (Automatic Electric Co.). June 4, 1925. Automatic exchange systems. - An impulse-sending arrangement, particularly for use in controlling twoco-ordinate finder-switches which are set by numerical impulses characteristic of a calling line, sends out a continuous train of impulses without any pause between the two series, the change-over from one magnet to the other being effected by the last impulse o f the first series. The arrangement comprises two counting-switches which are operated in parallel with the respective operating-magnets of the finder, and a sequence switch which is controlled by the last vertical impulse so as to direct the remaining impulses to the rotary magnet and is further controlled by the last rotary impulse to effect a switching-through operation at the finder. The production of impulses is controlled revertively by the finder magnets, each of which at the end of its stroke completes a circuit for a stepping relay which opens the original impulse circuit. In the system shown, an idle finder F, Fig. 1, is assigned by an allotter FA with which is associated impulse-sending mechanism, Figs. 3 and 4, common to a group of finders. The finder F is linked to a secondary hunting-switch SS, Fig. 2, which preselects an idle first selector FS, this operation also being controlled by the common apparatus, Figs. 3 and 4. The arrangement is such that the selector FS although preselected is not seized until a call actually comes in and is therefore available during this interval for seizure by secondary switches in other groups. The finders rest normally opposite their first levels and if a call is made by a line in this level the controlling sequence switch is operated immediately so that only the rotary magnet is controlled by the impulses. Control of finder F to seize calling line in the second level. When subscriber A (No. 35) removes his receiver, his line relay 3 closes digitdetermining circuits 18, 19 ; 16, 17 ; and also earths the common start wire 12 thereby operating relays 226, 225. Relay 226 completes a circuit 258, 85, 104 for relay 222 which earths conductor 82 and wiper 102 to mark the first selector FS busy. Relay 225 energizes relay 37 and at armature 254 completes parallel impulse circuits 263, 248, 280, 313, 274, 80 to the finder vertical magnet 34 and 249, 279, 312, 277, 243, 271 to the stepping magnet 301 of the vertical counting-switch VS. A further parallel circuit branching from the latter circuit over common terminal 321. leads 16, 17, terminal 292, and wipers 308, 314 is completed for stepping magnet 303 of the sequence switch SE. The vertical magnet operates to raise the wipers 31 - - 33 to the second level and sends back an impulse over lead 79 to stepping relay 224 which opens the impulse circuits. Magnets 301, 303, now advance switches VS, SE one step so that when the release of magnet 34 and relay 224 reclose the impulse circuits, the next impulse passes over leads 275, 81 to the rotary magnet 35 and over wiper 312 to the stepping magnet 302 of the rotary counting-switch RS. The operation of the rotary magnet 35 energizes relay 224 to terminate the impulse as before. Five impulses are thus transmitted to magnets 35. 302, the fifth impulse passing also over the circuit 254, 249, 312, 309, 295, 18, 19, 293, 311, 314 to the magnet 303. (The inclusion of wiper 309 of switch VS in this circuit prevents interference between two simultaneous calls in different levels). At the conclusion of the fifth rotary impulse, magnet 303 advances switch SF to its 3rd position in which relay 227 is energized over wiper 312 and completes a circuit 251, 244, 84, 50, 47 for relay 36 which (unless the line A has meanwhile become busy, in which case relay 36 is short-circuited over the test wiper 32) switches through from the calling line to the first selector FS and operates the cut-off relay 2. Relay 227 also completes restoring circuits over conductors 272, 273 for switches VS, RS in series with a relay 228 which maintains relay 227 operated until release is complete. In the 3rd position of switch SE, a further circuit 314, 276, 254 is completed for magnet 303 and upon the release of relays 226, 225, 227, the opening of this circuit causes the switch to move into its 4th position which is multipled to the 1st. Operation of allotter FA and preselecting switch SS. A branch of the circuit for the upper winding of relay 227 leads over contacts 252 and conductor 87 to the stepping magnet 77 of the allotter and upon the opening of this circuit when relay 225 releases, the wipers of the allotter are advanced one step. If the next finder is busy the magnet is again energized over its interrupter contacts 78 and a circuit 86. 267. 84 to the test wiper 75. When an idle link is seized, stepping magnet 104 is connected over the circuit 85. 260. 245. 82 to the test wiper 102 and the switch SS hunts until an idle selector is found. Call from line in first level. If a subscriber A' (No. 15) in the first level makes a call, his line relay 5, in addition to earthing the start wire 12 and closing the digit-determining circuit 14, 15, closes a circuit for relay 221 which opens the vertical magnet impulse circuit and completes a circuit 254, 249, 312, 277, 243, 281. 303, for driving the sequence switch SE into its second position in which rotary impulsing takes place as before. The finder off-normal springs 49 - - 51 are arranged to operate as soon as motion in either the vertical or rotary directions takes place. Busy arrangements. If all the first selectors accessible from a secondary switch SS are busy, relay 106 energizes in a chain circuit and causes relay 37 to operate and mark the finder F busy over contacts 48, 50. If all the finders associated with the allotter FA are busy, relay 229 operates, opens the hunting circuit of magnet 77 to prevent useless hunting, and energizes relay 227 to open the start circuit. Faults. A slow-operating relay 223 is connected in parallel with the impulsing circuit and normally does not have time to operate but if the magnets 34, 35 fail to close their contacts 40, 41, relay 223 energizes after an interval and closes an alternative circuit for relay 224 so that impulsing continues although at a slower rate. In case the switches VS, RS fail to restore within a given time, the relay 228 in the restoring circuit energizes relay 227 to open the start circuit and also operates a supervisory relay 231 to inform an attendant. Statistical metering; prematurely abandoned call. Meters M, M<1> indicate the number of times the switches VS, RS are operated uselessly. For a normal call from a level other than the tenth the meters are not connected up and for a call from the tenth level they are short-circuited over line-relay contacts. If, however, a calling loop is opened before impulsing is completed, the meters will be operated when the counting- switches pass respectively through their tenth positions.