An in-vehicle apparatus includes a first pulse generator configured to generate a first pulse in accordance with predetermined equipment before a data stream transmitted from the equipment is received; a second pulse generator configured to generate a second pulse based on the received data stream; an output device configured to output a warning sound based on the first pulse or the second pulse; and a switching device configured to output the first pulse to the output device before the data stream is received, and output the second pulse to the output device as of when the first pulse and the second pulse coincide.