Improvements in or relating to radio receivers employing crystal triodes

摘要

739,765. Transistor receiving apparatus. STANDARD TELEPHONES & CABLES, Ltd. April 14, 1954, No. 10998/54. Classes 40 (5) and 40 (6). In a detector circuit mounted in a telephone receiver case 17, the input is applied to the unbiased emitter-base circuit 3, 2 of a transistor, the receiver windings 9 being arranged in the collector-base circuit 4, 2 polarized from a bias supply 11. Positive-going half cycles of carrier from tuned circuit 5, 8 cause the emitterbase circuit to conduct, an amplified signal appearing in the collector-base circuit. Negative-going half cycles cut off the emitter current flow so that detection of the amplitude modulated carrier results. The telephone 9 may be shunted by a by-pass capacitor 12 and a protective resistor 10 included. In a modification, Fig. 4 (not shown), the base 2 is tapped on to the inductor 5 to provide positive feed-back. The aerial is attached to terminal 6 and battery to terminals 13, 14. Alternatively the battery may be mounted in the earpiece. The case 17 serves as an earth conductor connected to the wearer.