GB1144485A - Improvements relating to telephone instruments - Google Patents

Abstract

1,144,485. Sets. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 3 May, 1967 [10 May, 1966], No. 20673/66. Heading H4J. [Also in Division H1] A subscriber's instrument has a gravity switch mechanism provided with means for magnetically assisting its operation. A permanent magnet 2 (Fig. 2A) is mounted on the longer arm of a 14 : 1 ratio lever 4 adjacent the end on which an operating plunger (not shown) acts in the direction F. As the plunger is depressed and the lever 4, pivoted at 10, approaches a mild steel plate 6 the magnet 2 is attracted to the plate 6 with increasing force. The other arm of the lever 4 is coupled to the operating comb of a springset 12 and has a return spring 14. A residual gap 8 remains when the plunger is fully depressed and limits the attractive force to a value which can be overcome by spring 14 when the plunger is released. The strength and/or positioning of the magnet 2 on the lever may be adjusted. Alternatively the magnet 2<SP>1</SP> (Fig. 2B) is fixed and attracts the longer arm of a mild steel lever 4<SP>1</SP>. A non-magnetic stud 16 provides a residual gap 8<SP>1</SP>. In another example, a mild steel lever 4<SP>1</SP> (Fig. 2C) co-operates with a horseshoe arrangement of a bar magnet 18 and an L- shaped soft iron polepiece 20. A stud 16 provides a residual gap. The mechanism permits use of a lightweight handset having the hand grip extending from front to back across the instrument body and over the telephone dial.