Patent GB-401586-A (GB)
Title: Improvements in or relating to impulse transmitters for use in telephone systems
IPC: H04M1/677
Filed: 1933-04-11
Abstract: 401,586. Automatic exchange systems ; impulse transmitters. TELEPHON-APPARAT-FABRIK E. ZWIETUSCH & CO., GES., 6, Salzufer, Charlottenburg, Berlin. April 11, 1933, No. 10859. Convention date, May 17, 1932. [Class 40 (iv).] A dial type transmitter having facilities for preventing completion of a connection when certain digit combinations are dialled comprises a series of devices set in turn in accordance with the digits dialled and which, if the digits are characteristic of an unallowable connection, prevent the transmission of further impulses until the receiver is replaced. The devices, in certain positions thereof, operate spring sets which are interconnected to shortcircuit the impulse springs. The dial may be applied to a pay station in a system having different fees for various zones, and calls other than local may be time-controlled. Impulse transmitter. The shaft A of the dial carries loosely mounted rotatable discs S1-S3 having pins a1-a3 normally held against fixed stops b1-b3 by springs F1-F3. The discs are operated by pawls T1-T3 which are mounted to rotate with the dial and engage spring- restored cams K1-K3 pivoted to the discs S1-S3. On dialling the first digit, pawl T1 engages K1 which moves slightly to engage pin f1 on disc S1 which is thereupon rotated in accordance with the digit and held by dog PI. Normally, cam K1 is held in the full line position by a pin d1 which engages a fixed stop e. When, however, pawl T1 moves back to normal with the dial, K1 moves into the dotted line position so that it is not engageable by pawl T1 on subsequent diallings. On dialling the first digit pawls T2, T3 move cams K2, K3 one step in the counterclockwise direction without moving discs S2, S3, The pawls slip past the cams after moving them one step. On dialling the second digit, disc S1 is unaffected, pawl T2 engages cam K2 which comes up against pin f2 and drives disc S2 in accordance with the digit, the disc being held by dog P2. Cam K3 is moved another step by T3 without affecting disc S3. On dialling the third digit, S1, S2 are unaffected, cam K2 being rocked idly by pawl T2, but pawl T3 engages cam 'K3 which, by engagement with pin f3 drives disc S3 which is held by dog P3. The discs carry peripheral cams M, N of different heights at points corresponding to excluded digits and the cams operate spring sets Sp differently according to their height, e.g. cam N1 closes contacts I of Sp1, but cam M1 closes contacts I and II. The discs are released by switch-hook H when the receiver is replaced. Four digit sequences are dealt with by four discs S, and more than one spring set Sp may be used for each disc, the sets being arranged side by side and operated by cams arranged as will appear from the description of Fig. 4 below. Circuit arrangements, Fig. 4. The application is not limited to automatic pay stations but the circuits will be understood from the following description of a pay station in a zone system in which all calls except local commence with digit O. The dial discs S1-S4 carry cams represented by small circles which operate spring sets I-XII for the digits indicated alongside the circles. The unallowable numbers are not the same as those provided for in Fig. 1. For local calls, the dial springs nsi are short circuited over S1 (1) and coin-controlled contacts m4 until the requisite coins are inserted, contacts S1 (I) being unoperated since the initial digit is not O. The circuit is also blocked for various combinations commencing with digit O until the coins appropriate to the zone are inserted. For example, a call 0799 is blocked over S1 (I), S2 (III), S3 (V), S4 (X) until coin-contacts m1 are operated. Contacts m1 .. m4 open in response to coins of different values. Time-controlling arrangements. Local calls are not controlled, but on dialling the initial digit O for other calls, disc S1 operates contacts II to prepare a circuit for magnet SpM, the normal function of which is to connect up the coin collecting magnet KM when the receiver is hung up (HU2 closed). The circuit over S1 (II) for magnet SpM is completed, after say three minutes, by a time switch U. SpM opens the connection and is held from the exchange until release takes place.