Patent GB-1029565-A (GB)
Title: Signalling apparatus for telecommunication systems
Inventor: CRIPS DENNIS MICHAEL
IPC: H04M1/50
Filed: 1962-08-20
Abstract: 1,029,565. Subscriber's equipment. STANDARD TELEPHONES & CABLES Ltd. Aug. 15, 1963 [Aug. 20, 1962], No. 31871/62. Heading H4K. [Also in Division G4] A telephone dial is used as a multi-point switch, one or more signals being selected from several signals when the appropriate finger hole is turned to the finger stop, the selected signal or signals being transmitted when the appropriate finger hole is at the finger stop or during return of the dial to its normal position. The signals are audio-frequency signals. Two frequency selecting arrangements are described, either of which functions with any one of three arrangements for switching on the signal frequency generators, thereby providing six embodiments. In a seventh embodiment toggle mechanisms select the frequencies as well as switch on the generators. Frequency selecting arrangements.-The first frequency selecting arrangement uses four cams, one for each frequency. A finger plate 2 (Fig. 1) has secured to it, through a spindle, four cams A, B, C, D. Each cam has a set of raised portions, such as portions 1, 5, 6, 7 of cam A (Fig. 2). If the dial is set for digit 1, 5, 6 or 7 by rotating it in the usual manner to the finger stop 3, the corresponding raised portion of cam A operates its contacts 5 to select the corresponding required frequency A. The other three cams have differently located raised portions to select other frequencies B, C, D as required by the digit dialled. By designing cam A so that the raised portions correspond to digits 1, 3, 6, 7 all four cams can be cut to the same pattern and assembled on the spindle so that each pattern starts later than the preceding one. In the second arrangement (Fig. 3, not shown), a wiper is carried on the dial spindle and cooperates with an arc of pairs of fixed contacts. The wiper connects the appropriate contact pair in circuit when the dial is rotated so that the corresponding digit-hole is at the finger-stop. The contacts are connected to four generator circuits A, B, C, D so that a circuit is closed through the wiper at any digit position to select out of the four signals one or two signals appropriate to the digit. Switching of generators.-In the first arrangement a finger switch 6 (Fig. 4) similar to the normal finger stop 3 is integral with or fixed to an arm 7 pivoted at point 8. The end of arm 7 operates a pair of spring contacts 9. Arm 7 is normally held against a stop (not shown) by the back pressure of the movable spring contact of the contact pair or by a separate spring. In the second arrangement a cam 10 (Fig. 6) is fixed to the dial spindle and has a number of slots corresponding in angular position to the digit holes in the finger-plate. The cam 10 has a gap 19 corresponding to the home-position gap and lost-motion gap in the finger-plate. A toggle 11 has an enlarged upper end 13 and is freely pivoted at 14. A toggle arm 15 is pivoted at 16 in the dial case. A flat spring 17 anchored to the dial case co-operates with end 13 to urge toggle arm 15 towards a fixed stop 18. As the dial is set to a digit (e.g. digit 4) cam 10 rotates and the lower end of toggle 11 rides up on the cam edge. Arm 15 remains against its stop 18. When the dial is released, toggle 11 is trapped in the appropriate cam slot and, as the dial returns, arm 15 is forced upwardly to close spring contacts 12. As the end of toggle 11 is carried further, arm 15 returns to its normal position and contact springs 12 open. In the third arrangement a flat spring 17 (Fig. 7, not shown) bears on pins 15 of toggle 11 so that the toggle 11 is stable either in the " left-hand " position or in the " right-hand " position. When the dial is set to a digit (e.g. digit 4) cam 10 rotates so that toggle 11 rotates into the " left-hand " position against the pressure of spring 17. On release of the dial, toggle 11 is trapped in the cam slot (e.g. slot 4) and rotates into the " right-hand " position and in so doing the upper end of toggle 11 causes contact springs 12 to close for a short time. Contact springs 12 also close at the beginning of the setting, but at this time no signals are transmitted. Combined arrangement.-The same toggle arrangement is used as in Fig. 6 but four cams are used, one for each frequency. Cam A (Fig. 9, not shown) operates spring contacts for digits 1, 5, 6, 7. The four cams are secured to the dial spindle, are each associated with its own pair of contacts, and each pair of contacts is wired to energize the oscillator associated with that cam.