two-tone modulation

two-tone modulation

[′tü ¦tōn ‚mäj·ə′lā·shən]
(communications)
In teletypewriter operation, a method of modulation in which two different carrier frequencies are employed for the two signaling conditions; the transition from one frequency to the other is abrupt, with resultant phase discontinuities.
References in periodicals archive ?
A creepy carousel, first met in darkness, it periodically lights up and revolves, the bulbs on its ogee arches flashing in varying sequences, an automated drum kit that rides it beating time for the broadcast of a wheezy two-tone modulation on what sounds like the traditional carnival harmonium.