Subelement F: Receivers— Topic 49: Audio & Squelch Circuits
Question 3-49F3
Element 3 (GROL)What makes a Digital Coded Squelch work?
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.
Related Questions
3-49F1 What is the digital signal processing term for noise subtraction circuitry?3-49F2 What is the purpose of de-emphasis in the receiver audio stage?3-49F4 What causes a squelch circuit to function?3-49F5 What makes a CTCSS squelch work?3-49F6 What radio circuit samples analog signals, records and processes them as numbers, then converts them back to analog signals?