Automatic gain control
Automatic volume control (deprecated)
Circuits incorporated in the receiver and actuated by the received signal, which cause the gain of the receiver to vary substantially inversely as the magnitude of the radio-frequency input so as to maintain the output level substantially constant for a given modulation factor.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
centre of gravity
Celsius (previously Centigrade)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM