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dtmf programming
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PROGRAMMING WITH DTMF

There are multiple different DTMF sequences to program the same character, it depends on the equipment, system or application you are using and or programming. For example, on a standard 3X4-matrix keypad

the (1) key has no alphabetic value, only numeric. So no alphabetic characters can be programmed using the (1) key. The (2) key will usually have 4 different values, A, B, C and 2 whereas a differently designed keypad may have alphabetic value assigned to the (1) key, thus changing the alphabetic value of the (2) key.

When programming alphanumeric characters with DTMF, the tones are most commonly repeated until the specific character is displayed on the LCD screen or other type of monitor. Then either * or  #  is used to enter the current character and begin to program the next. The * and # keys are used for entering characters and deleting characters, most commonly * is used for deleting and exiting and # is used for entering.

           Not all equipment, applications or systems use DTMF to program words, they also use DTMF strings for different commands to perform certain functions on a system, application or piece of equipment.

    The table  shows the alphabetic values and functions assigned to each of the 12 standard numeric keys on a standard alphanumeric keypad.

 

 

Key

 

Character

 

Key

 

Character

 

Key

 

Character

 

1

 

1

 

2

 

A, B, C, 2

 

3

 

D, E, F, 3

 

4

 

G, H, I, 4

 

5

 

J, K, L, 5

 

6

 

M, N, O, 6

 

7

 

P, Q, R, S, 7

 

8

 

T, U, V, 8

 

9

 

W, X, Y, Z, 9

 

*

 

(Clear)

 

0

 

 

(Zero)

 

#

 

(Enter)