Patent GB-514178-A (GB)
Title: Improvements in or relating to automatic switches for use in telephone or like systems
IPC: H04Q3/00
Filed: 1938-04-28
Abstract: 514,178. Automatic exchange systems and switches. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., April 28, 1938, No. 12751. 'Convention date, May 10, 1937. [Class 40 (iv)] A switch, the control circuits of which resemble those of a Strowger-type switch comprises plunger-controlled spring sets arranged in levels 11 ... 16 and one plunger- and test wiper for each level. An actuating member set by the first digit tilts one of the wipers to enable it to engage the lowermost spring in each of the sets in its level when the wipers and plungers are moved across the contact field under escapement control during the secondary movement. Connection is completed by moving the actuating member towards the field to operate the plunger corresponding to the operative test wiper. Circuits are described for a group selector and a final selector. Construction of switches. When the switch is seized, an impulse is given to an escapement magnet 88 which allows a carriage carrying a plunger and a test wiper for each level to be moved one step along guide bars 39, 40. A detent 75 is thus brought into engagement with a vertical ratchet 67 which co-operates with a primary stepping magnet 63 to control the position of an actuating member 55 sliding in a member 46 carried by the carriage. The member 55 is normally in its highest position and on being moved brings test wipers 26 ... 31 successively into their operative position by means of studs 58, 59 &c. At the same time studs 61, 62 &c. are successively brought opposite the ends of the corresponding plungers 32 ... 37. Secondary movement. takes place under control of the escapement magnet 88 and the final connection is effected by energizing magnets 91, 92 which move the member 46, and with it the member 55, so that the selected stud 61, 62 &c. actuates the corresponding plunger. The switch is released by releasing these magnets and sending impulses to the magnet 89 which restores the carriage. When the latter reaches its normal position' it removes the holding detent 75 from the ratchet 67 which is then restored by a spring 70. Group selector, Fig. 3. Line and release relays 210, 220 pull up when the switch is seized and give an impulse to the escapement magnet 280, and the first digit is repeated to the vertical magnet 250 via series relay 230. The changeover of springs 137 by the preliminary impulse completes the current of the lower winding of the switching relay 200 to make it quick-acting. Owing to the change over of vertical springs 136, the relapse of 230 at the end of the digit makes a self-interrupting circuit for 240 which thus gives impulses to the escapement magnet 280 until its current is interrupted by the switching relay 200 which energizes the plunger actuating magnets such as 270. The line and release relays fall back. Final selector, Fig. 4. Operation of line and release relays 300, 310, preliminary operation of escapement magnet 380 and consequent operation of off-normal springs 156, and operation of vertical magnet 375, series relay 360 and.vertical off-normal springs 157 take place as in the group selector. In this case, however, the relapse of 360 completes a circuit over which the final digit is repeated to the escapement magnet 380 and relay 320 in parallel. Busy test and signal and control of ringing current. If the wanted line is busy, 330 pulls up as soon as the switch reaches the line, locks itself and sends back busy tone. If the line is idle, the relapse of 320 energizes 350 which locks and energizes the plunger magnets such as 385. The line is then rung in the usual way and the operation of ring-trip relay 340 completes the connection. Release. When the called party hangs up nothing happens, but release of 300, 310 by the calling party releases both switches. The plunger-controlling magnets are released and self-interrupting circuits are made for the relays 240, 370 which deliver impulses to the re-setting magnets 290, 390 until the switches are restored.