Hitachi, Ltd.

Mitsubishi Power, Ltd.

Naoya Fujita

Masamichi Yamada

Shigemitsu Higuchi

Tohru Sampei

Takuro Hashimoto

Kouichi Tomatsuri

Kohichi Tomatsuri

Koichi Akagi

Takanobu Ogata

An electrical discharge machining method includes selectively immersing only a portion of a workpiece in an electrical discharge machining liquid such that a machining object portion included in the portion of the workpiece is opposed to an electrode immersed in the electrical discharge machining liquid and applying an electrical discharge machining to the machining object portion by applying a voltage between the electrode and the workpiece in a state where the portion of the workpiece is selectively immersed in the electrical discharge machining liquid.

Electrical discharge machining method and electrical discharge machining device

A magnetic recording and reproducing apparatus comprises a source for producing test signals, a variable-gain amplifier, an equalizer, a recording bias generating circuit, a control unit for supplying control signals to the amplifier, equalizer and recording bias generating circuit, a memory and an operating circuit unit. The apparatus is automatically adjusted to each individual magnetic tape in use in such a manner that: a first test signal from the source is recorded on a magnetic tape with a preset bias control signal, the recorded first test signal is reproduced, the bias control signal is adjusted to provide a maximum HF saturation level and a minimum distortion to thereby determine an optimum bias control signal, and the proper bias control signal is fixed for said bias generating circuit; another test signal from the source is recorded on the magnetic tape with a preset gain control signal, the recorded other test signal is reproduced and is compared with a reference value at the operating circuit unit to provide an error signal, and the resulting error signal is fed through the memory to the control unit to renew the preset gain control signal for said amplifier. The adjustment of the frequency response control signal for the equalizer is effected in the same manner as the adjustment of the gain control signal.

Magnetic recording and reproducing apparatus automatically adjustable to

A tape recorder comprises, in its signal recording path, a variable gain circuit compensating the sound recording sensitivity of a magnetic tape and two variable equalizers compensating the frequency characteristic of the magnetic tape in the intermediate and high frequency ranges respectively. Reference signals at three different frequencies are successively supplied to the signal recording path to be recorded on the magnetic tape, and the signals of different reference frequencies are successively reproduced from the magnetic tape to be then arithmetically processed so as to optimize the gain of the variable gain circuit and the degree of frequency characteristic compensation by the first and second variable equalizers.

Tape recorder

Growing community of inventors

Yokohama, Japan

Naoya Fujita