Tuned radio frequency (TRF) is a type of radio receiver used in the early days of radio broadcasting. TRF receivers use a series of tuned circuits to select the desired radio station. Each tuned circuit is made up of a capacitor and an inductor, which are connected in parallel. The capacitor and inductor form a resonant circuit, which means that they have a natural frequency at which they resonate. When a radio wave with a frequency that matches the resonant frequency of the tuned circuit is applied to the circuit, the circuit will resonate and allow the radio wave to pass through. The output of the tuned circuit is then amplified and sent to the speaker.
