User Manual

3.11 DUAL-TONE MULTI-FREQUENCY KEYPAD

Dual-Tone Multi-Frequency (DTMF) is the system used by touch-tone

telephones. DTMF assigns a specific tone frequency to each key so a

microprocessor can easily identify its activation. The radio supports DTMF

using a microphone with an alphanumeric keypad (see Figure 3-11). This

allows for specific tasks such as entering a user ID and password, or selective

calling.

When a key on the DTMF keypad is pressed, a single low-pitched tone will be

heard from the microphone. The key tones are not adjustable.

NOTE

Although the “Q” is not shown on the 7 key, and the “Z”

is not shown on the 9 key on the DTMF keypad, both

letters are supported by the system. To enter a “Q” from

the keypad, press the 7 key 3 times (7, P, Q). To enter a

“Z” from the keypad, press the 9 key 5 times.

Because the Q and Z are recognized by the system, that

the number of presses to enter other characters from those

keys may be different. For instance, 5 key presses are

required to enter an “S” using the 7 key (7, P, Q, R, S).

If the key is pressed too many times, continue pressing the

key to scroll through the remaining characters and

returning to the first character. Remember to consider the

characters not shown on the keys.

Figure 3-11: DTMF Microphone Keypad