A "Westector" solid-state copper oxide diode was used for demodulation, which saved one valve and allowed use of an available type of pentode for the audio stage. The HT line was derived from a full wave rectifier. All valves were on International Octal sockets apart from the rectifier which was on a British 4-pin base. There were minor variations between set makers; for instance Philips used IF transformers with adjustable ferrite cores (so-called slug tuning) rather than the conventional trimmer capacitors. More than 40 manufacturers, such as Pye Ltd. and Marconiphone, made Utility radios. The manufacturer of a particular set was not readily apparent to the general public, although each manufacturer stamped a code letter on the radio to identify themselves to dealers. UK makers often used different designations for the same valve (tube), while octal tubes might be of USA origin. All valves in the Utility radio used standard designations prefixed by BVA (for British Valve Association). They were produced by valve makers such as Mullard, MOV, Cossor, Mazda and Brimar. Dealers, knowing the maker of a set and which valve manufacturer that maker used, could easily deduce which pre-war types these were and make warranty claims on the manufacturer.