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Graded (Analog) Code

A graded, analog code is one that varies continuously (no sudden steps), like a dimmer switch. A dimmer switch can vary the brightness of a lamp so it goes gradually from almost invisible to full brightness. Old phonograph records coded sound with a graded, analog code. The pattern of sounds were actually pressed into the record grooves. Another analogy is to a ramp, as opposed to a step. A ramp goes up gradually ("continuously"); a step goes up abruptly (you are at one level or the other).