Patent GB-368862-A (GB)
Title: Improvements in or relating to impulse transmitters for use in telephone or like systems
IPC: H04M1/272
Filed: 1930-12-17
Abstract: 368,862. Impulse transmitters. ASSOCIATED TELEPHONE & TELEGRAPH CO., 1033, West Van Buren Street, Chicago, U.S.A. Dec. 17, 1930, No. 38070. Convention date, Feb. 3. [Class 40 (iv).] In a keyboard sender, the actual impulsing is performed by the mechanism of a dial-type transmitter, such as that described in Specification 234,036, [Class 40 (iv), Telephones &c.], which is set by being coupled for varying periods to a motor. The digits corresponding to the operated keys are registered mechanically and subsequently, when the start key is operated, control in turn the setting movement of the impulse transmitter. The digit keys move in vertical slots 38, which are normally blocked by a toothed bar 39 until the operator removes her instrument from its cradle, when the bar is moved to the right, Fig. 1, through linkage to free the keys. The start key when operated acts on a slanting edge 40 to move the bar 39 to the left to lock the digit keys. The number register comprises a bank of pins frictionally mounted in a vertical frame 49, 50 which is adapted to be lifted by means of a ratchet 53 and a pawl 57 carried by a bracket 58 pivoted on the shaft 45. This bracket extends beneath all the keys, so as to be depressed as each key is operated, and its return movement under control of a spring 11 lifts the pin frame one step. A spring-controlled holding pawl 61 is provided for the ratchet 53. The keys are pivoted on the shaft 45, and the digit keys have upward extensions 66 with forward projections 67 which form a row corresponding to a row of pins in the pin frame. The first key depressed therefore causes a selected pin in the first row to be projected on the right-hand side, Fig. 3, of the pin frame, which is then lifted one step, and the next key depressed operates a pin in the second row in a similar manner, and so on. The start key has an upward extension 69 with an arm 80, which acts on the pawls 57, 61 when the key is depressed to allow the pin frame to drop to its normal position. A second arm 79 co-operates with the frame to prevent depression of the start key until a digit key has been operated. Operation of the start key, by means of a roller 71 on the extension 69, brings springs 77, 78 into engagement to close the circuit of the motor 12, while a catch 72 engages a pawl 73 to hold the key depressed. The main shaft 16 is geared to the shaft of the impulse transmitter 42 through a gear segment 103 and carries a spider one arm 23 of which, co-operates with a stop 28 on a lever 26 which is withdrawn when the start key is depressed, allowing a small initial rotation under the influence of the restoring spring of the transmitter 42. The arm 21 thereby shifts a member 24 to remove a shunt from the impulse springs at springs 30, 31, while the arm 20 strikes the end 125 of a pawl 121 normally bearing against a pin 115 on a spool 112, on which a rod 118 is eccentrically pivoted. The spool 112 rotates until the pin 115 again strikes the pawl 121, first under control of a spring 119 and then by engagement of the knurled part of the end 113 with a friction-wheel 129 mounted on the shaft 16 and driven by the motor 12, imparting a reciprocating movement to the rod 118 which bears against the bracket 58, thus lifting the pin frame one step to bring the first row of pins into position to control the setting of the transmitter 42. A lever 131 on the shaft 16 carries a pawl having three arms 137, 138, 139. When the arm 137 is struck by the pin 115 during the rotation of the spool 112, the arm 139 is moved into engagement with a ratchet 128 driven by the motor, thus coupling the shaft 116 thereto to set the transmitter 42, the movement being completed by the withdrawal of the arm 139 when the arm 138 engages the operated pin of the first row. Impulsing takes place during the return movement of the transmitter 42, and at the end of this movement, the arm 20 again strikes the pawl 121 to release the spool 112, and the cycle of operations is repeated. The pin frame is finally raised so that there is no pin in the path of the arm 138, and the shaft 16 then rotates until the arm 138 strikes a stop 144, but its return is prevented by a pin 105 on the segment 103 which moves past and engages the end of a spring 106. In the extreme position the segment 103 trips the pawl 73 to release the catch 72, allowing the start key to return to normal, while the arm 23 strikes the end 621 of the holding pawl 61, allowing the pin frame to drop. At the same time, the arm 22 restores the member 24 to shunt the impulse springs. The pin frame in dropping engages the end of a lever 108 which withdraws the spring 106 to allow the return movement of the shaft 16 until the arm 23 strikes the stop 28. To restore the operated pins, a lever 87 is lifted at the limit of the movement of the shaft 16, rotating a bracket 96 by means of a pin-andslot connection to move a restoring plate 99 laterally against the pin frame. The error key when depressed withdraws the pawls 57, 61 by means of the extension 68 to release the pin frame, while in its return movement the lever 87 is lifted by means of a pivoted arm 92 to restore the operated pins.