the early 1980s a number of higher extension levels were envisaged for the specification, based on ideas then being promoted for worldwide videotex standards (telephone dial-up services offering a similar mix of text and graphics). The proposed higher content levels included geometrically-specified graphics (Level 4), and higher-resolution photographic-type images (Level 5), to be conveyed using the same underlying mechanism at the transport layer. No TV sets currently implement the two most sophisticated levels. Level 1 (1976) The initial Broadcast Teletext Specification set out by the BBC, IBA, BREMA in September 1976: Alpha-mosaic characters (drawn using a 2×3 block matrix) characters (similar to some characters of the TRS-80 character set) spacing attributes fixed colour palette (red, green, yellow, blue, magenta, cyan, white over a black background) support for double height or flash effect 40 columns × 24 rows character grid Level 1.5 (1981) An extended version of level 1, with support for 13 extended character sets and other ASCII-like characters. Czech and Slovak English Estonian French German Italian Latvian and Lithuanian Polish Portuguese and Spanish Romanian Serbian, Croatian and Slovenian Danish, Swedish and Finnish Turkish This is the most common system and still used by most TV channels as of 2021. Level 2 (1988) World System Teletext Level 2 was introduced in 1988. New features were: Multi-language support 32 colour mode. Non-spacing attributes Allows re-definable characters (Level 2 was replaced by level 2.5) Level 2.5 teletext / Hi-Text (1995) Level 2.5 or HiText. was first broadcast in 1994 by the bilingual French-German channel ARTE. With Level 2.5 it is possible to set a background colour and have higher resolution text and images. The system was adopted initially by ARTE, ARD, ZDF, Bayern 3 and SwissTXT. New features of Level 2.5 teletext: Multi-language support Wider colour palette with re-definable colours (4,016 colour palette) Non-spacing attributes Allows re-definable characters Provides side panels for additional text or graphics in 16:9 TVs nexTView EPG The system has not been widely implemented, with only a handful of European state broadcasters supporting it. Television stations which are known to transmit Level 2.5 teletext in the late 2010s include: Netherlands: public broadcaster NOS (background colour on all pages, and a test page with hi-res graphics), France: France 3 Germany: ZDF (some pages), 3sat (some pages) Bayerisches Fernsehen (and formerly also now-renamed BR-alpha) (in the past on almost all pages, now only on some pages), phoenix (on some pages),