Patent GB-375799-A (GB)
Title: Improvements relating to selecting switches for automatic telephone and other selective systems
IPC: H01H63/20
Filed: 1931-03-17
Abstract: 375,799. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, PATTERSON, W. G., 68, Eltham Road, Lee, and GACHET, E. J., 12, Eatington Road, Leyton, all in London. March 17, 1931, No. 8197. [Class 40 (iv).] In a line switch the stepping magnet MC energizes initially over the calling loop and at the first step is connected over contacts. MC1 to an interrupter. Contacts MC3 are opened at the first step, while contacts MC4 are controlled by the stepping magnet. Relay T energizes when an idle trunk is found and changes over contacts MC2, while contacts MC1 are completely disconnected until the switch returns to normal. Relay T also withdraws the normal holding detent and inserts a temporary holding detent and thus controls the restoration of the wipers which is effected by means of a spring. When relay T falls back the contacts MC2 are disconnected until the normal position is reached. If the wipers are moved to the last position without an idle trunk being found, they are restored by mechanical means which also separate the contacts MC1. When the ,switch is seized from a final selector, relay T energizes in the usual manner, but the contacts MC1, MC2 are not affected. Construction. The stepping magnet 5 (MC) and relay 4 (T) are mounted on one side of a frame, while on the other side are mounted the rack 14 which carries the wipers and the various contact springs. The wipers may be adapted to enter a bare-wire multiple. The rack 14 is supported by a bracket 12 and is driven to the left against the action of a spring 19 by a pawl 31 carried by the armature 29 of the magnet 5. The armature 29 also controls contact springs 33 (MC4). An insulating block 47 on the rack normally bears against contact springs 74 (MC3), and these open at the first step. At the same time, a projection 70 rides on a bridge-piece 56 on the block 47 and thereby shifts outwardly a pair of contact springs 59, 60. Spring 59 makes with spring 62 (not shown) instead of with 61 (MC1) but spring 60 remains in contact with spring 63. When relay 4 attracts its armature 40, an arm 65 moves upwardly and lifts springs 52 away from springs 71 and into contact with the feeder wires 48 which are led along the underside of the block 47. It will be seen that the feeder wire leading to the test wiper is normally in engagement with the corresponding spring 54. Also a 'block 67 engages a pin 72 and lifts springs 59, 60 away from springs 62, 63 (MC1, MC2) and makes contact between springs 60, 68 (MC2). The arm 42 of the armature 40 inserts a holding detent 43, and through a lever 45 shifts the normal holding detent 36 to the side of the rack, where it is held until it is brought back by engagement with a cam in the normal position of the switch. On the release of relay 4, the detent 43 is withdrawn and the rack 14 is returned by the spring 19. Spring 68 is disconnected from spring 60, but it is so shaped that springs 59, 60 are moved sideways and are retained until the normal position is reached by the projection 70 slipping over to the upper surface of the bridge 56. In the last position of the switch, a pin 75 on the rack strikes the lever 45 and shifts the holding detent 36, thus allowing the rack to restore. A ramp on the bridge 56 engages the projection 70 and lifts springs 59, 60 away from springs 62, 63. Modification. If an arcuate bank is employed instead of a straight bank, the wiper shaft may be rotated through a pin-and-slot connection with the rack.