Explanation: Digital Coded Squelch (DCS) systems, often called CDCSS or DPL, operate by embedding a continuous stream of sub-audible **digital codes** within the transmitted voice signal. The receiver's squelch circuit is specifically programmed to detect and recognize a particular digital code sequence. When this exact digital code is present in the incoming signal, the squelch opens, allowing the audio to pass. If the digital code is absent or incorrect, the squelch remains closed, muting unwanted transmissions or noise. This method uses discrete digital patterns for selective listening, distinguishing it from analog tone squelch (CTCSS) which uses specific audio frequencies, and basic squelch which reacts to the presence of a carrier or the absence of noise.