Also known as custom ringing and priority ringing. 1. A network feature that allows the subscriber to (a) enter a list of telephone numbers, calls from which are announced with a special ringing tone, or (b) associate a ringing pattern with different directory numbers, all of which ring on the same physical line. Distinctive ringing is one of a suite of services of the public switched telephone network (PSTN) known as custom local area signaling services (CLASS). See also CLASS and PSTN. 2. A feature of voice telecommunications systems that uses distinctive tones to distinguish between internal and outside incoming calls. Distinctive ringing is a common feature of key telephone systems (KTS), PBX, and Centrex systems. See also Centrex, KTS, and PBX.