Released in 1987 at a price of £89, the Mode 7 Mark 1 Display Unit was a separate unit that connected to the Electron's expansion connector and featured a Motorola 6845 display controller and Mullard SAA5050 character generator to replicate the main elements of the BBC Micro's Teletext display solution. This only used 1 KB of memory for the display, with the expansion listening to display memory write accesses and buffering the data in its own memory. A ROM was included to extend the operating system to allow activation of Mode 7 as a genuine screen mode and to provide extra commands and to support keyboard shortcuts used on the BBC Micro to emit Teletext control sequences. To support the output of both the Mode 7 display and the existing video output, a lead connected the Electron's RGB output to the expansion, with the expansion providing only RF (television) output.