Wednesday, 3 June 2015

Teletext specs

Canvas: 40w x 24h character codes (80w x 72h 'pixels')
Colours: 7 (and black)

Broadcast Teletext Specification is here.

The Enhanced Teletext Specification document is here.

Did you know?

[Ceefax and ORACLE] were originally incompatible; Ceefax displayed pages of 24 lines with 32 characters each, while ORACLE offered pages of 22 lines with 40 characters each. In other ways the standards overlapped; for instance, both used 7-bit ASCII characters and other basic details. In 1974 all the services agreed a standard for displaying the information. The display would be a simple 40 × 24 grid of text, with some graphics characters for constructing simple graphics. The standard did not define the delivery system, so both Viewdata-like and Teledata-like services could at least share the TV-side hardware (which at that point in time was quite expensive).

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