The Doctor is In: Continuous Tone-Coded Squelch System

“In radio or wireless telephony, Private Line is a term trademarked by Motorola to describe their implementation of Continuous Tone-Coded Squelch System (CTCSS), a method of using low-frequency subaudible tones to share a single radio channel among multiple users.”

Learn about the technical background of this squelch tone system in the CTCSS, DTMF and More episode of the ARRL The Doctor is in podcast.