Advertised in late 1985, the Voxbox by Millsgrade Limited was an expansion connecting to the Electron's expansion connector that provided allophone-based speech synthesis, with driver software provided on cassette. The supplied software supported the definition of spoken words built up from the allophones - these allophones or sounds being stored in the expansion's own ROM - and for catalogues of words to be created and saved. A program was supplied that extended BASIC to allow the use of the synthesiser in user programs. The expansion used the General Instrument SP0256A-AL2 speech synthesis chip.