326,385. Clark, A. G., Heyne, W. O., and Plessey Co., Ltd. April 17, 1929. Receiving-sets, construction of.-A self-contained valve unit comprises a base 7 having a recess on its under-side, sockets for a detector valve 1 and for one or more amplifying valves 3, 45, mounted on the top of the base, coupling elements for the valves, and an HT-supply shunting- condenser mounted in the recess on the base. The valve coupling elements may comprise lowfrequency transformers high-frequency chokes, condensers 45, and grid leaks 47, which may be devoid of their usual protective casings. The base is perferably a one-piece structure of moulded insulating material and a wire gauze screen 17a may be moulded in the structure to screen the low-frequency transformers.