distinctive ring tones; ringtone differentiation
Refers to assigning different ringtones to different callers or groups, so you can tell who is calling by the sound.
I set distinctive ringtones for each friend on my smartphone.
Compound of 鳴り (nari, 'ringing') + 分け (wake, 'distinguishing'). The exact historical derivation is uncertain, but the word transparently describes the function.