CToneCadence
This Textual Convention defines cadence of the programmable tone to be played or detected. The format of cadence of the programmable tone is based on ITU E.180 Supplement 2. Cadence string consists of cadence units, digits, keywords and special characters. Cadence Units are digits where each unit is one second. No space is allowed in the cadence string. The keywords are 'on', 'off', 'CYCLES' and 'CONTINUOUS'. The special characters are '-', '*', '(', ')' and ','. 'on' - The number preceded this keyword is the duration of emission in second. 'off' - The number preceded this keyword is the duration of absence in second. 'CONTINUOUS' - The frequencies are sent out and stayed on indefinitely. An on-off Period is either the keyword 'CONTINUOUS' or a Cadence Unit followed by the keyword 'ON' or 'OFF'. '-' - Separator. It separates multiple on-off Periods. A Cadence List is a sequence of on-off Periods separated by the special character '-'. 'CYCLES' - When preceded by special character ',' and a number X, the Cadence List before the special character ',' is repeated X times. Cadence List - The parentheses are delimiters. It is used for the repetition. The entire Cadence List in the parentheses is to be repeated. Without the delimiter, only the first On-off Period is repeated. '*' - Repetition. When preceded by a number X, the On-off Period or the parenthesized Cadence List is to be repeated X times. ',' - Terminator. It terminates a Cadence List and announces the presence of the keyword, 'CYCLES'. When followed by a number X and then the keyword 'CYCLES', the preceded Cadence List is repeated X times For example, in United States, the cadence of confirmation tone is '3*100on-2*100off', the cadence of dial tone is '3*(100on-100off)-CONTINUOUS'. In United Kingdom, the cadence of payphone tone is '200on-200off-200on-200off'. Any thing other then the above notation is not supported.