There are several ways in which DTMF sequences can be used to program characters. The table below shows how alphabets and numerals can be transmitted using a standard DTMF sequence.
However, the sequence varies with the equipment or application that is being used. The above table shows the sequence on a standard 3X4 keypad where the digit 1 has no corresponding alphabet value and every other digit has three or four alphabets and one numerical digit associated with them. However, if a keypad were designed in such a way as to assign an alphabetic value to the 1 key, then all other values would change accordingly
When programming with DTMF, the tones are usually repeated until the specific character is displayed in the display panel of the equipment. Once a character is entered a * or # is entered before the next character is programmed. The * key is used for deleting characters and # is used to indicate a new character, though this can vary with the characteristics of the receiving equipment. Apart from programming words, DTMF strings can be also used to perform certain functions on an application or equipment.
references:
https://www.specialtyansweringservice.net/wp-content/uploads/resources_papers/dtmf-tone/Dual-Tone-Multi-Frequency-Signalling.pdf
However, the sequence varies with the equipment or application that is being used. The above table shows the sequence on a standard 3X4 keypad where the digit 1 has no corresponding alphabet value and every other digit has three or four alphabets and one numerical digit associated with them. However, if a keypad were designed in such a way as to assign an alphabetic value to the 1 key, then all other values would change accordingly
When programming with DTMF, the tones are usually repeated until the specific character is displayed in the display panel of the equipment. Once a character is entered a * or # is entered before the next character is programmed. The * key is used for deleting characters and # is used to indicate a new character, though this can vary with the characteristics of the receiving equipment. Apart from programming words, DTMF strings can be also used to perform certain functions on an application or equipment.
references:
https://www.specialtyansweringservice.net/wp-content/uploads/resources_papers/dtmf-tone/Dual-Tone-Multi-Frequency-Signalling.pdf
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