Patent GB-200206-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H01H63/30
Filed: 1922-04-08
Abstract: 200,206. Conrad, H. S. April 8, 1922. Automatic exchange systems and apparatus; selectors.-The wipers of an automatic switch fall by long and short steps under gravity to a wanted terminal set and on the completion of conversation are returned to normal by fluid-operated means. In the 10,000-line system described 500-point group selectors and 1,000-point connectors constructed according to the invention are used, the large contact banks permitting a connection to be set up in two numerical stages only, namely, by a group selector and a connector. The banks of the group selectors are arranged in 10 vertical columns of 50 terminal sets, the wipers first being rotated by ratchet-and-pawl mechanism, controlled by the thousands impulses, to select a particular vertical column, and then falling in a rapid continuous movement to within a short distance of an idle contact set, to which the wipers are then advanced more slowly step by step. The first continuous movement is stopped by a catch when a test wiper, positioned two or three short steps in advance of the other wipers, engages an idle line, or conversely a test contact of each contact set may be located in advance of the other contacts. The banks of the connectors are arranged in 10 vertical columns of 100 terminal sets, the wipers being first rotated by the hundreds impulses to select a vertical column, and then allowed to fall in long and short steps, under the control of the tens and units impulses respectively, to the wanted line. A piston working in a cylinder is mounted on the wiper shafts of the switches, at the end of conversation, air or other fluid being drawn from the cylinder above the piston head and causing the shaft and wipers to rise to their normal position. Construction of group selector, Fig. 2. The wiper arms 62, 63, Figs. 2, 4, 5, are connected to a block 61 sliding vertically in a tube 59, the wiper arms projecting through a flanged slot 169 in the side thereof. A shaft which controls the vertical movement of the wipers comprises a flat rod 49 terminating at its lower end in a ball 60, Fig. 5, which is rotatably held in the block 61 so that when the tube 59 is rotated by a ratchet wheel 29 and pawl 68 controlled by a rotary stepping magnet 28, the wiper arms are turned without turning the rod 49. The upper end of the rod 49 is furnished with a piston 44, which works in a cylinder 45 communicating through a normally closed valve 47 and tube 46 with a chamber maintained in a state of vacuum by a suction pump. The rod 49 is held in its normal upper position by a catch 52 which engages in a slot 50 in the rod and is withdrawn on the energization of a magnet 53. The rod 49 is also pierced by a series of slots 51 any one of which may be entered by a catch 57 pivoted on a lever 54. When the magnet 53 is energized the catch 52 is withdrawn and a projection 58 on the armature of this magnet prevents the catch 57 from entering a slot 51. The piston 44 is loose enough in the cylinder 46 to permit the rod and the wipers 62, 63 to fall rapidly when the catch 52 is released but not loose enough to prevent the piston from rising when the suction is applied by opening the valve 47. The terminal banks are arranged as shown in Fig. 6, the centre test terminals 74 being slightly longer than the line terminals. The rod 49 falls until an advance test wiper 73 mounted on the lower arm 63 engages the unearthed test contact of an idle line, whereupon the magnet 53 relapses and the catch 57 is permitted to enter a slot 51 which happens to be opposite to it at this time, thus arresting the fall of the wipers. The lever 54 also carries a rack 55 associated with an escapement operated by a self-interrupting magnet 56, which is energized after the advance test wiper 73 has engaged an idle line and allows the lever 54 and with it the catch 57 and the rod 49 to fall step by step until the test wiper proper 86 engages the test terminal previously engaged by the advance wiper 73. When the switch is first taken into use a starting magnet 27 is energized, and the notched end of a rod 42 pivoted to its armature 37 drops over the end of the stem of the valve 47. At the end of the conversation the magnet 27 is deenergized and the armature 37 retracts sufficiently to cause the rod 42 to open the valve 47 but not enough to release the rotary holding pawl 66. The piston 44 is now raised by suction until its upper end pushes up a pin 43 seated in the cylinder head. The pin 43 trips the rod 42 and the valve 47 is closed by its spring 48. In rising, the shaft rod 49 takes with it the catch 57 v;hi#h lifts the lever 54 and the rack 55 until they regain their normal positions, at which time a projection 151 on the armature 37 engages a tail piece 150 extending from the catch 57 which is thus withdrawn from the slot 51 in the rod 49. At the same time the holding catch 52 enters the slot 50 and prevents the rod 49 from falling back when the valve 47 closes. The complete retraction of the armature 37, when the rod 42 is tripped by the pin 43 at the end of the vertical restoring movement, causes a pivoted rod 65 to release the holding pawl 66 of the ratchet wheel 29 and permits a spring 64 to rotate the wiper arms 62, 63 back to their normal angular position. Construction of connector, Fig. 3. The manner in which the wipers 125, 126 are mounted and rotated, and the construction of the fluid-operated restoring apparatus is the same as that described with reference to the group selector. The flat . shaft rod 134 is held in its normal vertical position by a pawl 133 pivoted in a racked slide rack 132 mounted on a second slide 143 formed at its upper end with a rack and sliding in guides 144. The rod 134 is provided with two sets of five pins 137, 138 off-set above one another and cooperating with two pins 139, 140 mounted on the slide 132. The pins 137, 139 are mounted on one side and the pins 138, 140 on the other side of the rod 134 which passes through an opening in the sli'de 132. The slide 132 is stepped to the left by a pawl 131 pivoted to a lever 130 hinged to the slide 143 and operated by the tens stepping magnet 128. At the first step the shaft rod 134 is released by the pawl 133 and the pin 139 is brought below the lowest pin 137, the rod 134 dropping under gravity until these two pins come into contact, in which position the wipers 125, 126 engage the first terminal set in the vertical column previously selected by the rotary movement of the switch. At the second step of the slide 132 the pin 139 is moved to a position beneath the next pin 137 and the wipers fall to the eleventh terminal set. This operation continues the wipers falling the distance of ten terminal sets for each step taken by the slide 132, until at the sixth step the second pin 140 is brought beneath the lowest pin 138 of the second series after which the co-operation of the pins 140, 138 continues in a similar manner. When the desired tens group has been reached the units stepping magnet 141 controls an escapment 142 which permits the slide 143 to fall stepby-step taking with it the slide 132, the descent of which permits the rod 134 to fall by short steps until the wipers arrive at the wanted terminal set. At the end of conversation, the wipers are restored in the manner described with reference to the group selector, a collar 154 on the rod 134. engaging the slide 143 and raising it to its normal position, in which a tail on the holding pawl 104 engages a projection on the armature of the starting magnet 100, thereby releasing the pawl 104 and permitting the slide 132 to be returned to its normal position by a spring 155. The pawl 133 then enters its notch in the rod 134 and prevents the rod from falling when the suction is removed. Operation of system. A calling subscriber is connected in known manner by a 50-point line switch to a trunk 16, 17, Fig. 2, leading to an idle group selector. Response of the line relay 19 energizes the slow release starting magnet 27 and a slow release series relay 26, the former bringing into operation the pawls 66, 38, 39 betonging to the ratchet wheels 29, 40 of the main switch and the side switch, and the latter preparing the circuit of the rotary stepping magnet 28 which is energized on the transmission of the thousands impulses, the slow-release side-switch stepping magnet 30 being energized over the contacts 32, 33 on the first response of the magnet 28, and relapsing to move the side switch into its second position on the cessation of these impulses. In this position the magnet 53 is energized in a circuit over an earthed normal contact 74 engaged by the advance test wiper 73, conductors 72, 71, side switch arm 24, conductor 22, armature 20, and the wipers fall as described in a previous paragraph until the wiper 73 engages an unearthed terminal. The relay 53 and the side switch magnet 30 (energized at this time over contacts 77, 78) thereupon relapse and the side switch is moved to its third position in which a circuit is completed for the short step magnet 56, over an earthed test terminal (previously passed by the wiper 73 and now engaged by the wiper 86), conductor 85, side switch arm 34, conductor 82. The magnet 56 continues to step down the wipers until the wiper 86 engages the unearthed test terminal previously engaged by the advance wiper 73, whereupon the magnet 56 is de-energized and the side switch magnet, which was energized during the short stepping movement over contacts 87, 88, relapses and drives the side switch into its fourth position, in which busy earth is connected to the test wiper over the arm 34 and the calling line is extended to the seized trunk over the side switch arms 35, 36. The line relays 95, 96, Fig. 3, of a connector are now energized over the calling line, the relay 96 completing a circuit for the slow-release relays 100, 146, and the relay 95 preparing the circuit of the rotary step