Patent GB-129563-A (GB)
Title: An Improved Call Indicator for Telephone Systems Employing Automatic Switching Apparatus.
IPC: H04M3/64
Filed: 1918-12-30
Abstract: 129,563. Automatic Telephone Manufacturing Co., (Automatic Electric Co.). Dec. 30, 1918. Exchange systems and apparatus-An indicator for signalling a subscriber's number to an exchange operator is controlled by the impulse transmitter of an automatic system and comprises a plurality of number wheels rotatably mounted on a shaft and adapted to be actuated successively in a step-by-step manner by a single electromagnetically-operated pawl. The pawl is slidably mounted upon a pivoted carriage and is moved from one wheel to the next by an electro-magnetic escapement. The number wheels are held in their set positions against the action of springs by means of a comb, the teeth of which are normally held from the wheels by the action of a release wheel which is operated by the first set of digit impulses to allow the comb teeth to engage the wheels and to bring the pawl adjacent to the first number wheel. The release wheel is held in its operated position by a spring detent which is released when the receiver is placed on its hook and the pawl is returned to its initial lateral position, opposite the release wheel, by the operation of the hook switch. The number wheels and a release wheel 10, Figs. 2 and 3, are mounted upon a shaft 6, Figs. 1, 3, and 5. The wheels are zeroized by clock springs and are successively operated by a pawl 15 in a step-by-step manner. The pawl 15 is held normally adjacent to the release wheel 10 and is slidably mounted in a carriage which consists of transverse members 17, 18 and end members 20, 21. The carriage is oscillated about a pivot rod 19 by the armature 14 of a magnet 76, the armature 14 being provided with an arm 23 engaging a roller 22 on the member 21. The pawl 15 is stepped along the carriage to operate the various number wheels by means of an electro-magnetic escapement consisting of a cam 51 on the armature 44 of an electro-magnet 78 and a rack 41<1> mounted at one end of a lever 41. The armature 44 is provided with a roller 46 which engages a cam surface 47 as it rises thereby giving the armature an endlong movement to operate the rack 41'. The upper end of the lever is provided with a pin 48 which engages al slot in the pawl 15. The release wheel 10 is held in its cperated position by means of a spring detent 37, the position of which is controlled by a rod 38 attached at its lower end to the armature 40 of a magnet 77. The attraction of the armature 40 causes an arm 50 to lower the locking-pawl 49 of the lever 41 into engagement with an inner rack. The number wheels are held in their set positions by means of a comb 32, Fig. 1, the teeth of which are normally held out of engagement with the wheels by the release wheel 10 engaging an arm 33. The comb 32 is urged towards the wheels by means of a spiral spring 36, the end of which engages a tail-piece 34 of the comb. The. pawl 15 is urged towards the wheels by means of a spring 43 and is normally held away from them by a tail-piece 52 engaging a transverse member 16 which is lowered by the attraction of the armature 14 to allow the pawl 15 to approach the wheels. The armatures 14 and 40 are provided with projections 60 and 61 respectively adapted to operate the spring contacts of switches 72, 73, 74 and 74<1>, 75, Fig. 6. To make a call, the subscriber at the station A removes his receiver and his line is extended to the selector switch E through an individual line switch C. The impulse transmitter D is then operated to transmit the impulses of the first digit whereby the selector switch E is operated to extend the line conductors to the operator's cord circuit P, a portion only of which is shown. A relay 70 is then energized over the subscriber circuit from a battery B. The operation of the relay 70 energizes the mag net 76, the armature 14 of which steps around the release wheel 10 to allow the comb 3 to engage the number wheels and closes the circuit of the slow-release magnet 77. The armature 40 of the magnet 77 allows the spring detent 37 to engage the operated release wheel 10, closes a switch 74<1>, 75 in the circuit of the slow-release magnet 78, and by the operation of the arm 50 allows the locking-pawl 49 to engage the inner rack of the lever 41. Upon the first retraction of the armature 14 of the magnet 76 the circuit of the magnet 78 is completed at the contacts 72, 74 and the .armature 44 of the magnet 78 operates the lever 41 to move the pawl 15 along its carriage adjacent to the first number wheel. The intermittent attractions of the armature 14 step the first number wheel around in accordance with the second digit of the wanted number. At the end of the series of impulses the magnet 78 is de-energized by opening the contacts 72, 74 and the lever 41 is retained in position by the pawl 49. The remaining number wheels are similarly set. To restore the indicator, the relay 70 is de-energized by replacing the receiver at the substation A. The de-energization of the relay 70 causes the deenergization of the magnet 77 through the intermediary of the magnet 76 thereby raising the locking pawls 37 and 49 to release the wheel 10 and the lever 41. The comb is raised from the number wheels, which are returned to their zero positions under the actions of their clock springs, and the pawl 15 is returned adjacent to the wheel 10.