Which type of device enables an input signal to control an output signal?

An amplifier is designed to take an input signal and increase its power, voltage, or current to produce a larger output signal. This process allows the input signal to control the output signal effectively. By amplifying the input, the amplifier enhances the signal strength, making it suitable for various applications where increased output is necessary, such as audio devices or communications systems.

Amplifiers operate on the principle of controlling the output level based on the characteristics of the input signal. They can be configured in different ways, including linear or logarithmic responses, to meet specific operational requirements.

In contrast to amplifiers, the other devices listed function differently. A rectifier converts alternating current (AC) to direct current (DC) without increasing the signal strength. An oscillator generates a continuous output signal at a specific frequency, but does not primarily control output in response to an input signal in the same manner as an amplifier. A filter removes certain frequencies from a signal, which is dependent on the characteristics of the signal rather than amplifying or controlling the output based on the input.