Abstract: In an ink jet printer, a print head is provided with a plurality of nozzles. Each of piezoelectric elements is associated with one of the nozzles, and is provided with a drive electrode and a common electrode. A head driver generates a drive signal for driving the piezoelectric elements, and selectively supplies the drive signal to at least one of the piezoelectric elements to eject an ink droplet from at least one associated nozzle. A bias power source applies a bias voltage having a predetermined potential to the common electrode of each piezoelectric element.

Abstract: An overcurrent output protector is electrically connected to a constant-voltage switching power supply provided with a switching transistor which converts a DC voltage obtained by smoothing an AC voltage supplied from an AC power source into a cyclic pulse signal. In the overcurrent output protector, duty ratio monitor judges whether an ON duty ratio of the cyclic pulse signal is a predetermined ratio or more. A deactivator turns off the switching transistor in a case where the duty ratio monitor judges that the ON duty ratio is the predetermined ratio or more.

Abstract: An overvoltage output protector is electrically connected to a constant-voltage switching power supply which includes a switching transistor converting a DC voltage obtained by smoothing an AC voltage supplied from an AC power source into a cyclic pulse signal. In the overvoltage output protector, an overvoltage monitor whether a potential of the cyclic pulse signal is a predetermined value or more. A deactivator turns off the switching transistor in a case where the overvoltage monitor judges that the potential of the cyclic pulse signal is the predetermined value or more.

Abstract: In an ink jet printer, a print head is provided with a plurality of nozzles. Each of piezoelectric elements is associated with one of the nozzles, and is provided with a drive electrode and a common electrode. A head driver generates a drive signal for driving the piezoelectric elements, and selectively supplies the drive signal to at least one of the piezoelectric elements to eject an ink droplet from at least one associated nozzle. A bias power source applies a bias voltage having a predetermined potential to the common electrode of each piezoelectric element.

Abstract: A voice recording/playback apparatus includes a head unit which records a voice signal in a recording medium and for playing back a recorded voice signal from the recording medium. A playback head amplifier unit amplifies a playback signal output from the head unit. A voice output unit outputs a voice in accordance with the playback signal amplified by the playback head amplifier unit. A muting switch is provided between the playback head amplifier unit and the voice output unit. The muting switch cuts off a connection between the playback head amplifier unit and the voice output unit when a voice recording mode is performed by the head unit.