CToneFrequency
This Textual Convention defines frequency of the programmable tone to be played or detected. The format of frequency of the programmable tone is based on ITU E.180 Supplement 2. The frequency octet string is a combination of Frequency Expression, frequency conjuncture and frequency delimiter. Frequency Expression - The frequency expression is a single numeric value or a string of numeric values with the notation '+' or '/'. The numeric values are the frequency's decimal values in Hz. '+' - frequency conjuncture. The Frequency Expression to the left and to the right of this notation are emitted simultaneously. '/' - frequency delimiter. The Frequency Expression to the left of this notation is emitted before the Frequency Expression to the right. For example, the Payphone Recognition Tone of Australia is '1100+1750/750+1450', which means frequency 1100Hz and 1750Hz are emitted simultaneously, stopped for a period of time, followed by the simultaneously emission of 750Hz and 1450Hz.