Electronic active components include a large variety of military and avionic tubes, projection tubes, microwave tubes- including magnetrons, klystron amplifiers, travelling wave tubes (TWTs) and backward wave oscillators (BWOs).

BSL also stocks a wide range of both British and American parts and components as well as semiconductors and integrated circuits, some of which are no longer manufactured. All parts are NATO coded.

Spares are held for most communications systems, broadcast and defence systems, navigation aids, radar systems, data links of all types and industrial instrumentation. BSL can locate solid-state valve equivalents and transistor equivalents where they exist.