PURPOSE: To eliminate the need for a slide switch, to reduce the cost and to make the size small by applying switching operation to a switching transistor(TR) based on a sound volume control signal and selecting a prescribed signal level from each divided signal level.

CONSTITUTION: A control section 55 is provided with a sound volume storage means 55a storing prescribed sound volume information and a sound volume control means 55b outputting a sound volume control signal in response to the sound volume information based on a sound volume switching signal, and a signal level selection means 61a consists of a switching TR selecting a prescribed signal level based on the sound volume control signal. That is, the sound volume control means 55b reads sound voltage information stored in the sound volume storage means 55a based on the sound volume switching signal sent by the key operation on an operation panel, for example, and outputs a sound volume control signal in response to the sound volume information. A signal level selection means 61d based on the sound volume control signal selects a prescribed signal level by switching operation of the switching TR from plural divided signal levels. Thus, a slide switch for signal level changeover is not required and the device is made small.