Patent GB-190709923-A (GB)
Title: Improvements in Electric-switching Mechanism for Sending a Predetermined Number of Current Impulses.
Inventor: ROBERTS HOMER JOHN
Filed: 1907-04-29
Granted: 1908-02-20
Abstract: 9923. Roberts, H. J. April 29. Telephone systems; telephone calls. -Relates to apparatus for sendinga predetermined number of currentimpulses to line, applicable in partyline telephone systems and for analogous purposes. The current - impulses are produced by a rotary interrupter, the line-connexion being controlled by a ratchet-member which is displaced through the required angle to send the desired number of impulses, and is then automatically returned to its zero position by electro-magnetic mechanism. In its zero position, the ratchet-member breaks the line-connexion or reverses the polarity of the impulses sent to line, so that, after a station has been selected by a determined number of current-impulses, the bell of that station can be rung by impulses of reverse polarity. Fig. 1 is a plan and Fig. 2 an end view of the apparatus. The shaft ,11 carries at one end a ratchet-wheel 12, co-operating with a pallet 28 mounted on the armature 8 of the magnet 2, and at the other end a setting-dial 38 having a number of apertures 42 in which can be inserted a pin 41 on the setting-arm 39 loosely mounted on the shaft 11. The hub 12, Figs. 2 and 6, of the ratchetwheel is provided with two conical recesses 14, 14<1> adapted to engage the wipers 22, 23 on the contact-springs 16, 19. These recesses are arranged diametrically, but are longitudinally offset relatively to each other, so that the wiper which co-operates with one recess will not engage the other. The contact-springs are properly spaced by studs 26, 27. The spring 35, which, with the pallet 28, effects the return of the ratchet-wheel to the zero position, is connected to the collar 33 fixed nn the shaft 11, and to the collar 34 mounted loosely on the shaft. 11 but prevented from turning with the shaft by an arm 36 which engages a stud on the base-plate 1. In order that the initial impulse, which may be incomplete, may not be sent to line, means is provided to ensure that this initial impulse is sent through the magnet 2, thus operating the ratchet-wheel so as to close the line-circuit. This means consists of a split sleeve 47 held in light frictional engagement with the shaft 11 by the spiral spring 48. One section 47<1>, Fig. 4, of the split sleeve carries an arm 50 which normally engiges a contact-spring 58, thus closing the line-circuit, but when the shaft 11 is turned manually by the setting-arm 39, the sleeve sections and the arm 50 are moved a slight distance until the arm engages a stop 55 and is arrested by it. The first return step of the ratchet-wbeel again brings the arm 50 into contact with the spring 58 to close the line-circuit. Fig. 8 is a diagrammatic view of the apparatus, as used in a party-line telepbone system. C, D represent the ringing keys of the cord circuits c, d. Assuming that the calling-plug has been inserted in the required jack, the operator rotates the setting-arm 39, Fig. 1, inserts it in the aperture 42 having the desired number marked above it. and then rotates the dial and arm together until the pin 41 engages the stop stud 44. The contact between the arm 50 and spring 58 is thus broken as before described, and the actuating-springs 16, 19 engage the springs 17, 20. The ringing key is now depressed, closing a circuit from the brush b of the generator B through the contacts 19, 20, magnet 2, wires 59, 50, 64, contacts 63, 62, wires 65, 59<1> to the constantly-closed pole of the generator. The energizing of the magnet 2 allows the shaft 11 to return one step, thus closing contact 50, 58, so that when the brush b<1> engages the conducting part of the pole-changer, current flows through the contacts 17, 16, 50, 58, wires 68, 72, contacts 70, 71, to the sub-station apparatus and back to the gene rator through the contacts 61, 62, and wires 65, 59<1> as before. When the brush b receives current, the magnet 2 is again energized, and the ratchetwheel rotates one step. Current impulses are thus sent alternately to line and through the magnet B, until the ratchet-wheel is returned to its zero position, when the wipers on the springs 16, 19 enter the recesses in the hub 13 and interrupt the line-circuit and also the circuit of magnet B. As the contact 18 is connected to the brush b, impulses of reverse polarity then flow through the contacts 18, 16, 50, 58 to line as before and ring the subscriber's bell. The ratchet-wheel has several teeth omitted from its periphery at the point corresponding to the zero position in order that after the last impulse sent to line, the wipers may readily enter fully into the recesses and thus certainly reverse the connexions.