GB889542A - Improvements in or relating to telephone dials and to telephone subscribers apparatus incorporating telephone dials - Google Patents

Abstract

889,542. Impulse transmitters. GENERAL ELECTRIC CO. Ltd. July 20, 1960 [July 30, 1959], No. 26215/59. Class 40 (4). In an impulse transmitter of the dial type, an auxiliary spring set is provided whose contacts are actuated only when the return motion of the finger-plate is from a predetermined digit; the said contacts short-circuiting the impulsing contacts except when the predetermined digit is dialled. The impulse transmitter and its normal operation is exactly the same as that described in Specification 518,721. When the predetermined digit, i.e. 9, is dialled a member 11 engages a pin 9 projecting from one face of an auxiliary cam 8, which is free to rotate at one end of shaft 1, and so causes cam 8 to rotate. In so doing, cam follower 14 which is attached to contact spring 12 of the auxiliary springset 6, falls into the depression 15 on cam 8 and contacts 7 are separated so removing the short-circuit across the impulse contacts 4. During the return motion of the dial, nine impulses are sent to line, the member 11 then engaging pin 10 so that cam 8 is returned to its normal position. If the digit 0 is dialled, cam follower 14 rides over a projection 16 on the auxiliary cam 8 so that impulse contacts 4 are again shortcircuited. Spring 17 does not of itself store sufficient energy to return cam 8 to normal from one of its two off-normal positions but it does ensure that the return to normal is rapid once it has been initiated by the engagement of member 11 with pin 10. A keyoperated contact (Fig. 3, not shown), may be placed in series with the auxiliary contacts to allow unrestricted use of the telephone to privileged subscribers.