Patent GB-564320-A (GB)
Title: Improvements in or relating to electrical signalling systems
IPC: H04M1/515
Filed: 1943-03-19
Abstract: 564,320. Electric selective signalling systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. (Associated Electric Laboratories, Inc.). March 19, 1943, No. 4491. [Class 40 (i)] [Also in Group XXXIX] Selection, e.g. in an automatic exchange system, is dependent on the ratio of the durations of two signalling impulses and not directly on the durations. The system has the advantage of known systems in which selection is determined by the duration of a single impulse rather than by the number of impulses in a train without the necessity for synchronous apparatus at two stations. Construction of number sender. Operation of any of the digit keys closes a pair of contacts 41, 42 individual to the key and rotates a shaft 12 through 90 degrees by engagement of a pawl such as 34, with a ratchet disc, such as 37, on the shaft. In its lowest position, the key rocks and is then locked by a lever 26. Rotation of shaft 12 in this way gives a complete rotation to a shaft 18 secured to one end of a helical spring 16, the other end of which is secured to a gear-wheel 43 mounted to rotate on shaft 18 and normally prevented from doing so by a hook 57. The wheel 43 is geared to a wind vane or centrifugal brake and carries brushes 24, 25 which co-operate with contacts 61 ... 69, 60, 71 and a conducting ring 72. When the lever 26 is rocked, it releases the gear-wheel 43 which then rotates through 360 degrees, unlocking the operated key at the end of its travel and then remaining locked by the hook 57. The line circuit is normally completed over contact 71 and is thus interrupted when the wheel 43 begins to rotate. It is completed momentarily when the brushes reach the terminal corresponding to the depressed key via the springs 41, 42 controlled by that key and is then interrupted again until the gearwheel has completed its rotation. Construction of switch. Wiper arm 121 is pivoted to the framework and is moved by a block 118, which engages it through a pin-andslot arrangement, in two directions at right angles by rotation of shafts 110, 111 against the action of restoring springs 191, 190. These shafts are rotated by a roller 150 which is driven by an individual or common motor and is brought into engagement with a roller on one or the other of the shafts by one of two magnets 153, 154. The armatures of these magnets is normally latched in its central position by an auxiliary armature 172 which is pivoted to the main armature and is drawn clear when either magnet is energized. Brake magnets 176, 177 stop the rollers when necessary. Circuit arrangements. Line relay 211 is operated over the loop and energizes 212 which energizes both brake magnets of the switch. When the subscriber operates one of the digit keys, the first of the resulting line interrupters energizes magnet 153 in series with relay 215. Magnet 153 releases one of the brake magnets and couples the driving roller to shaft 110 which is thus rotated, moving the carriage 112 to the right. Release relay 212 now has a holding circuit over off-normal springs 185, 186. On the re-operation of the line relay at a point determined by the depressed key, 153 is released and 213 pulls up and locks so that when the line circuit is interrupted again a circuit is made over 214 for the other magnet 154. Shaft 111 is thus rotated and drives shaft 117 moving block 118 vertically and so moving the wipers over the bank. When the line circuit is re-made, magnet 154 is released and both brake magnets are energized. The relapse of 214 after a brief interval extends the subscriber's line wires and a connection to relay 210 to the wipers. Relay 220 in the circuit of the wanted party pulls up over the loop and energizes 223 which rings the line and energizes 221, which locks up and cuts off 223. 210 in the selector circuit pulls up also, disconnecting the relay which remains held locally. When the calling subscriber hangs up, 220 is released and also 221, 210, 211. Magnet 154 is again operated in series with 214 and lifts block 118 until it engages a rod 138 over which a circuit is completed for relay 216 which locks and disconnects the clutch magnet and both brake magnets whereupon the switch is restored. On restoration of the off-normal springs, the remaining relays fall back. In the case of premature release, the carriage moves to an extreme horizontal position and makes a circuit over bar 138 for releasing the switch. A similar action takes place if the number sender is faulty.