dual-tone multifrequency (DTMF) signaling
dual-tone multifrequency (DTMF) signaling: In telephone systems, multifrequency signaling in which standard set combinations of two specific voice band frequencies, one from a group of four low frequencies and the other from a group of four higher frequencies, are used. (188) Synonyms multifrequency pulsing, multifrequency signaling. Note 1: DTMF signals, unlike dial pulses, can pass through the entire connection to the destination user, and therefore lend themselves to various schemes for remote control after access, i.e. , after the connection is established. Note 2: Telephones using DTMF usually have 12 keys. Each key corresponds to a different pair of frequencies. Each pair of frequencies corresponds to one of the ten decimal digits, or to the symbol "#" or "*", the "*" being reserved for special purposes. Note 3: The standard signal frequency pairs transmitted by DTMF equipment used by the public exchange carriers are as follows:
| Button or Digit | Frequencies (Hz) |
| 1 | 697/1209 |
| 2 | 697/1336 |
| 3 | 697/1477 |
| 4 | 770/1209 |
| 5 | 770/1336 |
| 6 | 770/1477 |
| 7 | 852/1209 |
| 8 | 852/1336 |
| 9 | 852/1477 |
| 0 | 941/1336 |
| * | 941/1209 |
| # | 941/1477 |
Note 4: Tactical telephones have 16 keys, the extra 4 being used for precedence. For DSN (Defense Switched Network) the signal frequency pairs transmitted for the ten decimal digits and the * and # are the same as those used by the public exchange carriers. The additional four keys, corresponding to four different frequency pairs and the precedence, are as follows:
This HTML version of FS-1037C was last generated on Fri Aug 23 00:22:38 MDT 1996