A filter circuit is an electronic circuit designed to allow certain frequencies of signals to pass while blocking others. It is commonly used in audio systems, radio communications, and signal processing to improve the quality of the output signal. Filter circuits can be categorized into three main types: low-pass, high-pass, and band-pass filters, each serving different purposes based on the frequency range they target. These circuits utilize components such as resistors, capacitors, and inductors to achieve their filtering effects. For example, a low-pass filter allows signals below a certain frequency to pass through while attenuating higher frequencies. By effectively managing signal frequencies, filter circuits play a crucial role in various applications, including audio equipment, telecommunications, and data transmission.