ABSTRACT
Some amplifiers and the more sophisticated mixers are fitted with a ‘signal-present’ indicator
that illuminates to give reassurance that a channel is receiving a signal and doing something
with it. The level at which it triggers must be well above the noise floor, but also well below the
peak indication or clipping levels. Signal-present indicators are usually provided for each
channel, and are commonly set up to illuminate when the channel output level exceeds
a threshold 20 dB below the nominal signal level.
