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:
Jun. 30, 1987
Filed:
Nov. 07, 1984
Hitachi, Ltd., Tokyo, JP;
Abstract
An audio signal transmission system having a noise reduction circuit, which includes a transmission medium such as a magnetic tape to be used to transmit a digital signal converted from an input audio signal and thereafter to output the audio signal reproduced from the digital signal, a digital signal transmitter having a pulse-code modulator and demodulator (MODEM). The noise reduction circuit includes a compressor for compressing the dynamic range of the input audio signal according to the detection level obtained by detecting at least the high-frequency components thereof in order to supply the output from the compression to the digital signal transmitter and an expander for expanding the dynamic range of the demodulated signal from the transmitter according to the detection level of at least the high-frequency components thereof. The transmission system has a low-pass fitler which limits the frequency band of the input signal to be supplied to the dynamic-range compressor to at most half the sampling frequency of the MODEM and thus permits the noise reduction circuit to compress and expand signals supplied thereto in the same frequency band without causing any erroneous operation.