Patent GB-190822439-A (GB)
Title: Improvements in Selective Signalling Devices
Inventor: MANNY IRA F
Filed: 1908-10-22
Granted: 1909-02-18
Abstract: 22,439. Manny, I. F., and Binzel, A. V., [trading as Manny Signal Co.]. Oct. 22. Switches.-A selective apparatus for momentarily closing the local call bell circuit of a subscriber in a party-line telephone or other system is actuated by clock-work under the control of an electromagnetic step-by-step escapement device operated by current impulses from the calling station. The ratchet-wheel 28, 29 of the escapement is connected to its clockwork-driven shaft 24 by means of a spring, so that, when the escapement wheel of each instrument on the party line is stopped on the completion of the series of signalling impulses, the spring connexion between the escapement and the shaft 24 allows the shaft to continue to rotate. When the shaft has rotated a certain fraction of its revolution, in an interval of time sufficiently long to allow the longest series of impulses to have been transmitted, a cam gives the anchor pawl 30 of the escapement a lateral movement, thus freeing the ratchet-wheel 28, 29, which now follows up the shaft and rotates with it, until an arm 24 on the shaft re-engages with the anchor pawl 30, which has by this time come back to its normal position under the influence of its cam. But at the station that is being called, the anchor pawl, in its lateral movement to free the escapement wheel, engages with a catch 44 mounted rotatably on the wheel and holds this catch against the force of a spring. The escapement wheel continuing in its motion, a contact 51 on this wheel touches a contact 52 on the pawl-held catch, thus completing the local bell circuit. The catches 44 of all the other instruments of the line are not engaged by the pawls 30, the catches of these stations simply moving with the escapement wheels so that the local call circuits of these instruments are not completed. In order that the catch 44 may be released after the contacts 51, 52 of the called instrument have touched, the catch is mounted on an eccentric on the escapement wheel, which draws the catch out of engagement with the pawl after the contact between the pieces 51, 52 has been made. All the parts are now free and rotate until they re-assume their original positions. If the number of impulses sent over the line is less than the number required to make a call at any station, the pawl 30 engages with the catch 44, and it is necessary to free the catch before the contacts 51, 52 have had time to touch. For this purpose, the eccentric on which the catch 44 is mounted is pivoted at 47, and a bar 60 mounted on the eccentric normally occupies a position one tooth in front of the catch 44. If then the number of impulses transmitted is less than the number required to make a call, the pawl 30, on receiving its lateral movement, engages first with the bar 60, and the eccentric is rotated on its pivot 47 to such an extent that, as is shown in Fig. 3, the catch 44 is freed from its engagement with the pawl 30 before the contact 51 has had time to touch the contact 52. It is desirable that, after the escapement-wheel has been freed, the shaft 24 should rotate more rapidly so as to complete the cycle of operations quickly. For this purpose, the motor is braked so long as the escapement is held by the pawl, that is so long as the escapement wheel lags behind the shaft to which it is flexibly connected. But immediately the escapement is freed, this lag disappears and two cams mounted respectively on the escapement wheel and on the motor shaft interact to remove the brake from the clockwork, which then returns the parts to their original positions at fullspeed.