GB317574A - Improvements in or relating to radio receiving apparatus - Google Patents

Abstract

317,574. Preen, A. June 13, 1928. Composite units.-A plurality of low-frequency .valve coupling-elements are housed in a single casing with external terminals. As shown in Fig. 3, the unit comprises a rectangular casing with a flange F round its base on which a series of terminals are mounted. The unit encloses the coupling-elements for a detector valve followed by two low-frequency amplifiers. The plates of the three valves are connected to the terminals p<1> - - p<3>, and the grids of the second and third valves to terminals g', g<2>. The inter-valve coupling-elements comprise plate resistances 7, 8 coupling condensers 9, 10 and grid chokes 12, 13 ; whilst the output circuit of the last valve includes a choke 14 and a condenser 11 leading to the loud-speaker terminal l. Hightension is applied at the terminal h and grid bias at terminals b<1>, b<2>. A high-frequency choke is included in the detector plate circuit. The coupling-condensers may be connected to tappings on the chokes 12, 13 or to their grid ends. Similar units for two valve stages may be arranged in cylindrical cases, and may include a transformer output instead of the choke-capacity arrangement shown. Chokes may be substituted for the plate resistances 7, 8 and grid-leak resistances for the chokes 12, 13. The various terminals are labelled to indicate their correct connection, and a celluloid sheet showing the circuit diagram may be mounted on the top of the casing. The units are particularly intended for adding stages of amplification to an existing set.