A signal processor includes an input unit, an analog-digital converter, a control circuit, and a reservoir unit. The input unit receives a first analog signal. The analog-digital converter converts the first analog signal to a first digital signal. The control circuit detects the first analog signal or the first digital signal and outputs a control signal for extracting a part of the first analog signal or the first digital signal. The reservoir unit receives at least a part of the first digital signal and operates in synchronization with at least a part of the control signal.