Hitachi, Ltd.

Toshiba Lighting & Technology Corporation

Shigeru Okada

Takao Arai

Kouichi Tomatsuri

Hiroshi Toeda

Iwao Aizawa

Koichi Hirose

Hitoshi Imamura

Katsuyuki Ide

Jyunichi Nakajima

Masaharu Aridome

A magnetic recording and reproducing apparatus including a recording head, reproducing heads and reproducing pre-amplifiers each mounted on a rotating cylinder for allowing recording and reproducing operations at the same time, in which two signal channels are defined by first and second double azimuth heads each made up of two reproducing heads and first and second integrated circuits are arranged on the rotating cylinder in close proximity to the first and second double azimuth heads, respectively. Each of the integrated circuits includes two pre-amplifiers corresponding to two reproducing heads of the first or second double azimuth head and selectively outputs one of two amplified reproduced signals from the above pre-amplifiers which is higher in signal level, and a head discrimination signal is added to the output signal. The input part of each reproducing pre-amplifier is constructed to perform a differential operation, and one of the output signals of the first and second integrated circuits is selectively sent to a fixed side through a single transmission means in accordance with a control signal supplied from the outside. The magnetic recording and reproducing apparatus having the above construction can be made small in jitter and crosstalk, and can reduce the number of elements for transmitting signals between the rotating cylinder and the fixed side.

Magnetic recording and reproducing apparatus

A discharge lamp comprises a cylindrical lamp casing substantially formed of a metallic material, a transparent glass plate air-tightly fitted to one of the opened end of the lamp casing, a sealing stem air-tightly closing the other opened end of the lamp casing, and a pair of cathode and anode elements sealed in the lamp casing together with discharge gas. The lower portion of the lamp casing may be made in square or circular structure and may be composed of a metallic cylindrical portion extending to a half way of an axial length of the cylindrical lamp casing and a cylindrical transparent glass portion tightly surrounding the outer periphery of the metallic cylindrical portion of the further extending portion and having a front end extending to the sealing stem closing the other end of the lamp casing. The discharge lamp further comprises a member for regulating discharge generated between the paired cathode and anode elements and the interior of the discharge regulating member is divided into a plurality of luminous chambers so that the discharge lamp operates as a fluorescent lamp. The improved structure of the discharge regulating member can improve the light distribution characteristic of the fluorescent lamp.

Discharge lamp

A gain control circuit comprising a pair of transistors constituting a differential amplifier, and a pair of resistors each connected to the emitter of one of the transistors and having a sufficiently great resistance value compared with 1/gm of the transistor in the transistor operating range, the resistors being connected to a common regulated current supply to supply the halves of control current from the regulated current supply to the respective transistors, a pair of diodes are connected to the collectors of the respective transistors as a load, and a first variable resistor means is disposed in the current path traced from the diodes to the regulated current supply via the transistors and resistors for compensating fluctuation of the diffused resistance of the diodes. Further, a second variable resistor means is disposed in the base bias circuit for the transistors for compensating fluctuation of the base-emitter voltage of the transistors.

Gain control circuit

Disclosed is a gain control circuit which comprises a gain control section including as its essential component a differential amplifier with which diodes or transistors arranged to act as diodes are connected as a load, and a control signal section including a logarithmic compression circuit and an exponential expansion circuit and providing a control signal for control of the gain of the gain control section. A temperature compensation circuit having a temperature dependence cancelling both the temperature dependence of the gain control section and that of the control signal section is provided in the bias circuit for the transistor in the last stage of the control signal section, so that the desired temperature compensation for the entire gain control circuit can be achieved at a single point.

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Yokohama, Japan

Shigeru Okada