1986, Permanent Memory Systems announced a second processor product for the Electron, the PMS-E2P, as a self-contained cartridge for use with the Plus 1 containing a second 2 MHz 6502A processor plus 64 KB of RAM, priced at £89. This was based on a product originally developed by John Wike of Jafa Systems. Available as a kit or in assembled form, it could even be adapted to connect directly to the Electron's expansion connector, thus avoiding the need to even have a Plus 1 expansion, although this would require the user to find other solutions for attaching peripherals. The implementation of the interface between the Electron and second processor was said to adhere closely to Acorn's recommendations, noting that any hardware or software compatibility issues were likely to be the fault of other vendors not similarly adhering to Acorn's guidelines. Sound system expansions Despite the Electron having only limited sound generation capabilities, few expansions were offered to overcome the machine's limitations. Millsgrade Voxbox 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. Sound Expansion cartridge Originally announced in 1987 by Project Expansions to be priced at around £40, the Sound Expansion cartridge could be fitted in a Plus 1 (or compatible) slot and provide sound output equivalent to that of the BBC Micro, with Superior Software's Speech bundled as a "limited offer". A product of the same name and with similar functionality was subsequently sold by Complex Software for around £55, employing its own adjustable speaker in the cartridge unit. Superior Software had announced a version of Speech for the unexpanded Acorn Electron in 1986, but this was never released. Hybrid Music 5000 Hybrid Technology's Music 5000 was adapted and released by PRES for use with the 1 MHz bus of the Advanced Plus 5 expansion, with the Music 5000 itself priced at £113.85. The only functional differences between the Electron adaptation and the original BBC Micro unit