Patent GB-190400833-A (GB)
Title: Improvements in and relating to Telephone Systems.
Inventor: REDMON HOPE
Filed: 1904-01-12
Granted: 1904-06-02
Abstract: 833. Redmon, H., Halls, R. L., Conway, R. H., and Smith, N. F. Jan. 12. Telephone systems.-Each subscriber on a party line is provided with the selective switching-instrument shown, in which normally his telephone and call instrument is short-circuited by the contact of two springs 11, 12. An operating wire is provided in addition to the telephone wire and the return wire or earth. An operator at the exchange can move a sliding contact over a row of numbered contacts, to send impulses of current from a battery in one direction through the operating circuit, which includes the electromagnet 9 of each selector ; the armatures 22 of these electromagnets turn ratchet-wheels 19 and tappets 48 to open the short-circuits of the telephone &c. instruments successively, until the desired number is reached, while all other selectors are locked. A subscriber can open the short-circuit of his own telephone &c., in order to call the exchange, by holding up a rod 36, unless the line is already in use, in which case the rod 36 cannot be raised. The exchange operator can send a reverse current to re-set all the ratchet-wheels and tappets to the starting position, if they have got out of order. In each selector, the armature 22 is carried by a pivoted lever 10, movable by the electromagnet 9 in opposition to a spring 24 ; the movement by the spring is normally limited by an arm f engaging a stop g. The lever 10 carries a pawl 17 to turn the ratchet-wheel 19, in opposition to the action of a spring 53, connected by a cord to a drum on the ratchet-wheel ; reverse turning is prevented by a stationary detent 18. The tappet 48 is secured by a screw to the ratchet-wheel, and is set differently for each subscriber ; it acts directly on the short-circuiting spring 12. When the subscribers' rod 36 is raised, it turns a lever 13 about a pivot 32 to displace the spring 12. The lever is then temporarily held up by a pin engaging a notch A in the armature lever 10. When the ratchet-wheel 19 is turned, a notch in a disc attached to it passes from under an arm 39 of a stop 38, which then stands over a pin on the lever 13 so that this cannot be lifted. A pointer 60 may be connected to the ratchet-wheel to move over a dial, indicating by whom the line is in use. When a conversation is finished, the central operator sends current impulses through the operating circuit until all the ratchet-wheels have turned as far as possible. A projection on each ratchet-wheel then engages and turns an adjacent loose plate 16, a part of which raises the operating pawl 17 from the ratchet-wheel. On another current being sent, the pawl 17 turns the loose plate so that another part of it raises the detent 18 from the ratchet-wheel, which is then returned to its starting position by the spring 53 ; when the current is stopped, the armature lever 10 and pawl 17 move back, releasing the loose plate, which falls to its non-operative position. For re-setting all the ratchet-wheels and tappets, each armature lever 10 carries a straight permanent magnet c on end pivots, and two projections d on one end of this magnet are situated near the armature 22 ; the magnet carries the stop arm f. In normal working, the direction of current in the electromagnet 9 is such as to attract that projection d which retains the arm f in position to engage the stop g. If a reverse current is sent, the magnet c turns, with the arm f, and the spring 24 thereupon moves the lever 10 further than usual, so that a pin on it bears on a curved part, not shown, of the detent 18, which lifts the pawl 17, releasing the ratchet-wheel 19 ; the ratchetwheel is then returned to its starting position by the spring 53. In a modification, the permanent magnet is carried by stationary pivots behind the yoke of the electromagnet 9, and its arm extends forward to engage the armature lever 10.