Patent GB-218789-A (GB)
Title: Automatic switching arrangements for telephone exchanges and the like
IPC: H01H63/20
Filed: 1923-05-08
Abstract: 218,789. Coventry Automatic Telephones, Ltd., and Collyer, J. E. May 8, 1923. Automatic exchange systems; selectors.-In a selector having groups of terminals arranged in the same plane, a reverse spring drive is employed, the driving pawl being controlled by the stepping magnets to pick up a number of teeth of the ratchet on the wiper shaft at each impulse to select a group of terminals, and then to pick up only one tooth at a time. Means are described for varying the number of terminals in each group, and a single stepping magnet with an auxiliary magnet may be used. Circuit arrangements are described in which the release relay can only become energized in the normal position of the selector. Circular arc form, Fig. 2. The bank 1 consists of 10 groups of 11 terminals, and the frame 3 carries an adjustable wiper unit 6 secured to the arm 7 of the ratchet 8. The arm 22 carrying the driving pawl 23 is pivoted on a shaft 20 and is integral with a bracket 21 fixed to the armature 13 of the long stepping magnet 10. Upon energization of the magnet 10, the arm 22 moves backwards until it strikes a stop 43, so that the pawl 23 picks up 11 teeth of the ratchet 8, and upon de-energization, the ratchet is advanced by the driving spring 26. The armature 15 of the short stepping magnet 11 is attached to a U- shaped bracket 28 pivoted on the shaft 20 and carrying an extension 29 which co-operates with interrupter contacts 31, 32. Upon energization of the magnet 11, the bracket 28 engages a pin 44 on the bracket 21 and thereby causes the pawl 23 to pick up one tooth of the ratchet 8, which is advanced upon de-energization. The driving pawl 23 and a retaining pawl 34 are both withdrawn through a lever 38 when the release magnet 35 is energized, and the ratchet is restored to normal by a spring 40 under control of a governor if necessary. Means for varying the number of terminals in a group, Fig. 5. The arm 101 carrying the driving pawls 107 is limited in its stroke by the engagement of an extension 106 with stops such as 105 which may be inserted in holes 103 in the ratchet 102 according to the number of terminals in each group. Panel form, Fig. 8. The ratchet 171 slides on rods 155 which support the frame 153 carrying the stepping magnets 157, 161 and the release magnet 179. The arm 165 carrying the driving pawl 166 is controlled by the armatures 159, 163 substantially as in Fig. 2, and the driving pawl and the retaining pawl 175 are withdrawn upon energization of the release magnet 179 through a rod 183. The ratchet is guided by rollers 172, 173 and a shield 174. The stroke of the arm 165 is limited by an escutcheon 184. Control by a single stepping magnet, Fig. 9. The escutcheon 207 which limits the stroke of the driving arm 205 is pivoted to the frame, and upon energization of an auxiliary magnet 211 is rocked through an angle determined by a screw 209 and slot 210, so that the stroke is limited by an edge 220 instead of by the edge 218. Circuit arrangements, Fig. 4. The release relay 58 energizes over the off-normal contacts when the line relay 57 operates, locks itself to the test wire 64 and connects up a relay 59 which closes the circuit of the long stepping magnet 57 to whidh impulses are repeated at contact 65, relays 58, 59 being held at contact 66. At the end of the impulse train, relay 59 releases, the off-normal contacts being operated, and connects up the short stepping magnet 52 in series with the high-resistance switching relay 56 which is short-circuited as long as the test wiper engages earthed terminals, but operates when an idle line is found to stop hunting, switch through the talking conductors and temporarily ground the test wire 78. Upon release of the succeeding switch, relay 56 falls back and connects up the release magnet 53. The test wire 64 remains grounded until the selector reaches normal.