Volex TTX 2000a
Volex TTX 2000a Teletext-Telesoftware Adaptor from Volex Electronics (a divison of Volex Group plc). Teletext offers one-directional data transmission, broadcast via television signal. The Volex TTX 2000a was offered for ZX Spectrum, BBC, and Amstrad CPC.
As the name says, the device supports both viewing Teletext pages, and downloading Telesoftware (ie. computer programs encoded in Teletext pages).