Definition
Pulse code modulation is a method of converting an analog signal — such as voice or sensor data — into a digital form by sampling the signal at regular intervals and representing each sample as a numeric code transmitted as a sequence of pulses.
Plain English
A way of turning a continuous signal, like a voice, into a stream of numbers so it can be sent or recorded digitally.
Context Anchor
Seen in aircraft electronic equipment manuals, especially when describing digital audio, data recording, or signal processing.
Derivation
Pulse refers to the short bursts of electrical signal used to send the coded information. Code refers to the numeric values that represent each sample. Modulation means changing a signal to carry information. Together: encoding information as a coded sequence of pulses.
Why Pilots Care
Most modern avionics, digital voice radios, and flight data recorders rely on PCM to carry clean, accurate signals. It is the reason digital cockpit audio and data links are far less prone to noise and distortion than older analog systems.
Analogy
PCM is like taking many quick snapshots of a moving needle and writing each snapshot as a number. Put the numbers back in order, and the changing information can be rebuilt.
Intuition Check
PCM is not a radio call or a cockpit procedure. It is a way electronic equipment represents information as digital pulses.
Example Sentence 1
The flight data recorder uses pulse code modulation to store sensor readings as digital values.
Example Sentence 2
Flight data is converted by pulse code modulation before transmission to the ground station.