- telephone dialing in which tones or tone pairs are utilized to represent the available keys. dual-tone multi-frequency, for instance, uses tones which are a mixture of two frequencies, with each combination identifying the 0--9, *, and # keys found on most touch-tone phones. 2. Tone dialing (1) using a keypad, as opposed for instance, to the tones generated by a modem. Also called touch-tone dialing.