PURPOSE: To solve a problem that an acoustic equipment reproducing an entire audible band and an accessory equipment should be connected by two cords when a signal at a specific frequency band is reproduced.

CONSTITUTION: An acoustic equipment 1 is provided with a means mixing a signal at other frequency band than a specific frequency band with a full band signal, and an accessory equipment 2 is provided with a detection means automatically turning on a power supply circuit of a specific frequency band reproduction amplifier by detecting a mixing signal and with a filter cutting off other frequency signal than a specific frequency band from the mixing signal and applying a signal at the specific frequency band to a specific frequency band reproduction amplifier, then the acoustic equipment and the accessory equipment are connected by one cord 11, through which a signal to be reproduced and a signal used to turn on/off the power supply circuit of the specific frequency band reproduction amplifier at the accessory equipment side are transmitted.