The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 06, 1984
Filed:
Oct. 18, 1982
Hitachi, Ltd., Tokyo, JP;
Abstract
A modulator-demodulator suited to record an audio signal in a recording medium in the form of a frequency-modulated signal and to demodulate the frequency-modulated signal is disclosed. It includes a voltage-controlled oscillator, a switching circuit for changing one of two input frequency-modulated signals toward a control input of the voltage-controlled oscillator, and a phase detector for detecting a difference in phase between the frequency-modulated signal reproduced from the recording medium and the output signal of the voltage-controlled oscillator. In a recording operation, an input audio signal is supplied to a control signal input terminal of the voltage-controlled oscillator through the switching circuit, and the VCO acts as a modulator for carrying out frequency modulation. In a reproducing operation, the output signal of the phase detector is supplied to the control signal input terminal of the VCO through the switching circuit to form a demodulator having a phase locked loop configuration, and the frequency-modulated signal reproduced from the recording medium is demodulated by the demodulator. A single VCO is used as the VCO for forming the modulator in the recording operation, and is used as the VCO for forming the demodulator having the phase locked loop configuration in the reproducing operation.