magenta or white. The 1. Broadcast audio distribution is based on a sampling rate of shape of the characters is usually based on a 7 X 5 dot matrix, with 32kHz to provide a 15kHz audio bandwidth, with 14 bit linear a refinement known as character rounding. As many as 24 rows of (uniform) coding. the standard sized characters can be fitted on a page, and each row 2. Professional recording studios use a sampling rate of 48kHz can have up to 40 characters. Each page can carry about 150 to 200 equivalent to 1920 audio samples per video frame (625 line, words. 25Hz frames) or 2000 audio samples per frame for 24fps film, The specification also allows the option of characters of twice the with 16 or 20 bit coding. height of standard characters. Larger sized characters and also 3. Compact disc records (masters) have a sampling rate of drawings are made by assembling small illuminated rectangles, 44.1kHz (CD/EIAJ/RDAT replay only, 14 or 16 bits). each one sixth the size of the space occupied by a standard character, and these too can be in any of the six colours or in white. Part or all It is generally accepted that 16 bit/sample coding offers satisfac- of each page can be made to flash on and off (usually once per tory quality, but for signals prior to level control, or combined second), to emphasise any particular item. signals having a very wide dynamic range, longer data words are The page background is usually black, although the specification required of 20 bits or more per sample. allows the editor to define different background colours for part or Interface units permit conversion between sampling rates of all of the screen. Also, at the teletext editor's discretion, text can be 32kHz, 44.1kHz and 48kHz. Rate conversion between 44.1kHz and enclosed in a black window and cut into the normal picture. Further- 48kHz is rather more difficult than 32kHz to 48kHz. Cascading a more, certain receiver designs allow the whole page (sometimes in number of sample rate converters (SRCs) tends to degrade the white only) to be s