Kenwood TH-F6A Service Manual page 22

13. DTMF Table
697 Hz
770 Hz
852 Hz
941 Hz
Dual Tone Multi-Frequency, or DTMF is a method for instructing a telephone switching system of the
telephone number to be dialed. The DTMF dialing system was developed by AT&T in the 1960s and
was deployed within the AT&T telephone network as a way for customers to direct calls using in-band
signaling. This was marketed by AT&T under the registered trade name Touch-Tone®.
The DTMF system uses eight different frequency signals transmitted in pairs to represent sixteen
different numbers, symbols and letters. This table shows how the frequencies are organized. The
frequencies used were chosen to prevent any harmonics from being incorrectly detected by the receiver
as some other DTMF frequency. The transmitter of a DTMF signal simultaneously sends one frequency
from the high-group and one freqency from the low-group. This pair of signals represents the digit or
symbol shown at the intersection of row and column in the table. For example, sending 1209Hz and
770Hz indicates that the "4" digit is being sent.
Dual Tone Multi-Frequency (DTMF) Table
1209 Hz 1336 Hz
1
GHI
4
PRS
7
* OPER
High-Group
Frequencies
1477 Hz
ABC DEF
2
JKL MNO
5
TUV XYZ
8
0
1633 Hz
A
3
B
6
C
9
# D
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