GB791782A - Improvements in and relating to devices for the transmission of series of electricalpulses - Google Patents

Abstract

791,782. Impulse transmitters. VIERLING, O. Jan. 16, 1956, No. 1380/56. Class 40 (4). An impulse transmitter, particularly described as applied to a telephone instrument comprises a setting member 25 that is moved from an initial position by means of a spring 23 to a set position determined by the depression of one of a number of push-buttons 28 and is returned from the set position to the initial position by means of a stepby-step mechanism which at each step generates an impulse. The push-buttons 28 are mounted in a circular arc about a shaft 18 and are carried between two plates 13 and 27. The setting member 25 comprises an arm fixed to a ratchet-wheel 19 freely rotatable and axially slidable on the shaft 18. The ratchet 19 may be driven by a relay 14 carrying a driving pawl 16 working in conjunction with a retaining pawl 20. A disc 35 fixed to the shaft 18 carries pins 39 and 40 which may engage with small tolerance in holes in the plate 13 and also carries a longer pin 41 permanently engaged in a much larger hole 42. While the disc 35 is in the position shown in Fig. 4, pin 41 is held by a spring 44 in an extreme clockwise position in the hole 42 so that the pins 39 and 40 do not register with the holes in plate 13 and the push-buttons cannot be depressed as they engage the periphery of the disc 35. When idle, the setting arm 25 is held by ratchet 19 adjacent the pin 41, and when relay 14 is energized by lifting the telephone instrument receiver, ratchet 19 is pushed round so that arm 25 forces pin 41 to an extreme anti-clockwise position, as shown in Fig. 5, in which pins 39 and 40 register with the holes in plate 13 and the push-buttons can be depressed. At the same time a pressure block 53 on shaft 18 is turned with pin 41 and operates contacts 54a, 54b, Figs. 5 and 9, to hold relay 14 energized. When a push-button is depressed, the disc 35 and shaft 18 are displaced with it, and a collar 50 abutting the setting arm 25 pushes the ratchet 19 axially out of alignment with the pawl 16 and detent 20 which ride on a bevel 51 as shown in Fig. 6. This frees the arm 25 which is turned by spring 23 until stopped by the pin 30 on the depressed push-button. When released the push-button is returned by a spring 33 while the shaft 18 and disc 35 are returned by a flat spring 49 mounted on a bridge-piece 38 and bearing on the end of shaft 18. The ratchet is returned into engagement with pawl 16 and detent 20 by the straight portion of the spring 23 anchored to post 24. As soon as disc 35 is returned, pins 39 and 40 move out of alignment with the holes in plate 13 relocking the push-buttons and releasing the contacts 54a, 54b, to connect up relays 14 and 61 in a selfinterrupting circuit as shown in Fig. 9. The holding circuit for'relay 14 is broken by contact 54a and the relay falls back.slowly due to resistor 57. At the same time relay 61 is energized and interrupts itself to fall back with a release time determined by a resistor capacity slug. Relay 14 restores first and when relay 61 restores later both relays are re-energized. Variation of the release times of relays 14 and 61 controls the mark space ratio of pulses produced by contacts 21a. A lamp 67 may indicate the transmission of each pulse. Stepping of relay 14 returns arm 25 to its initial position to engage pin 41 and rotate disc 35 and shaft 18 whereupon relay 14 is held operated by contacts 54a and the pushbuttons are unlocked. The mechanism may then be reset for the transmission of another digit train by pushing another button.