Having two tones or sounds; characterized by duality of tone or sound.
From bi- 'two' + tonus (from Latin tonus, from Greek tonos 'tone') + -ous. Descriptive of something that produces or exhibits exactly two tones.
Binotonous systems appear in everything from sirens to bird calls—some creatures and machines specifically evolved or were designed to use just two distinct tones for maximum clarity and distance transmission.
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