Patent GB-270055-A (GB)
Title: Automatic telephone system
IPC: H04Q3/00
Filed: 1925-11-02
Abstract: 270,055. Baron, H., (Aldendorff F.). Nov. 2, 1925. Automatic exchange systems. - In a long and short step spring-driven selector operated directly by incoming impulses, a relay 18 which pulls up at the beginning of each odd impulse and falls back at the beginning of each even impulse prepares a circuit for the power magnet M<1> involving a front contact 13 of the line relay and groups of alternate terminals such as 21, 34 for the tens digit and 52, 53 for the units digit. Movement corresponding to a particular impulse thus does not take place until the end of that impulse, and if the calling party hangs up without dialling the wipers are not moved at all. The ringing generator 61 is connected over common condensers 62, 63 to the talking wipers and over a parallel path to the supervisory relay 69 which cuts off the ringing current and provides talking current for the called party. The power magnet is shunted bv a condenser to make it quick-acting. Specification 254,373 is referred to. Line relay 10 energizes release relay 16 when the connector is seized. The first impulse of the tens digit energizes relay 18 over its left-hand winding in series with the control magnet M<1>, which however is unable to pull up until, at the end of the impulse, the left-hand winding of relay 18 is short-circuited over 13. 26. Magnet M<1> then releases the wipers and magnet M<1> is held energized by the long terminal 33. Relay 18 remains energized over its right-hand winding until the second impulse arrives, whereupon it connects the terminal 34 on which the wipers have been stopped to the front contact 13 of the line relay. Consequently the end of the second impulse causes the wipers to take a further long step. The third impulse re-energizes relay 18 and causes a further long step and so on. At the end of the digit, relay 41, which was energized over 15. 19 and provided a holding circuit for relay 18 (left hand winding), falls back and energizes relay 37 over off-normal springs 43. Relay 37 locks up and connects the impulse wires 28, 35 to alternate terminals in the row of wiper 29, instead of to the terminals 21, 34, &c., and gives control of the magnet M<1> to wiper 29. Rewinding magnet M<2> is energized when relay 41 pulls up and springs 43 change over, and moves the cam 49 but not sufficiently to close contact 2<n>. The units impulses control the selector in the same way as the tens impulses, but since there are no long terminals such as 33 in the row of wiper 29 the switch moves in short steps. Relay 41 at the beginning of the digit re-energizes Magnet M<2> and cam 49 closes springs 2n. At the end of the digit relay 41 falls back to complete the test circuit. Ringing current. If the line is idle, switching relay 57 short-circuits a part of its winding and connects up to the ringing generator 61, which is shunted periodically at 67 to provide a silent interval. When the called party replies relay 69 pulls up over the loop to battery 68 and locks itself and energizes a back release relay 81 which locks up to the line relay contact 14. Release. When either party hangs up, relay 16 falls back owing to the short-circuit at 84 or disconnection at 15 and releases relay 57. The release is not completed until the calling party releases relay 10, whereupon magnet M<1> is permanently energized over 15, 90, 91 until the wipers reach normal and the contact 91 consequently is opened. When the wipers reach normal a projection 121 on the shaft closes the contacts 122. 123 to complete an interrupter circuit for the rewinding magnet. When the spring is fully rewound a projection 125 moved by the spring barrel tilts the member 127, which carries the spring 123 to disengage the latter from the projection 121. The rewinding circuit is thus opened, and since the projection 125 is now past the member 127 the latter returns to the position shown.