Before revision: A tuned radio frequency receiver (or TRF receiver) is a type of radio receiver that is composed of one or more tuned radio frequency (RF) stages followed by a detector (demodulator) circuit to extract the audio signal and often one or more audio frequency amplifiers .
After revision: A tuned radio frequency receiver (or TRF receiver) is a type of radio receiver that is composed of one or more tuned radio frequency (RF) stages followed by a detector (demodulator) circuit to extract the audio signal and usually an audio frequency amplifieramplifier .