6K V1.02 03-16-91
57
TONE CODES
When entering tone frequencies for CW, beep, or paging messages, a
tone code
is required. A
tone code is a 4-digit number that may be either taken from the Tone Code Table or calculated.
The Tone Code Table was created to simplify your programming efforts by listing frequencies from
100 Hz to 3 kHz (in 5 Hz increments), and the appropriate tone code for each frequency. (Note that
most radio systems have a response of 300 Hz to 3 kHz, and will not pass tone frequencies outside
of this range).
If you wish to program a tone frequency that is not listed in the Tone Code Table, you will need to
calculate its tone code. (This is particularly true of paging tones, which are specified to tenths of
Hertz). To assist you in calculating your tone codes, the following explanation is offered.
Tone codes are actually 4-digit numbers representing the period of the tone sine wave in
microseconds. To determine your tone code, simply take the reciprocal of the tone frequency. It is
easily done on a calculator: Enter 1,000,000, and then divide this number by the tone frequency in
Hertz. The quotient, rounded off to a 4-digit whole number, is the tone code. If the result is 999 or
less, you must insert a leading zero. Here are some examples:
Example 1:
The tone frequency is 1200 Hz. What is the tone code?
Dividing 1,000,000 by 1200 yields
833.3
, so the tone code is
0833
.
Example 2:
The tone frequency is 398.1 Hz. What is the tone code?
Dividing 1,000,000 by 398.1 yields 2511.9, so the tone code is
2512
.
