| English thesaurus | |||
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| Dual Tone Multiple-Frequency (The signaling system used in telephones with touchtone keypads, in which each digit is associated with two specific frequencies) | |||
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| DTMF | |||
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dual-tone : 18 phrases in 4 subjects |
| Communications | 4 |
| Electronics | 8 |
| General | 2 |
| Information technology | 4 |