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:
Feb. 28, 1978
Filed:
Sep. 08, 1976
Applicant:
Inventors:
Takuji Mukaemachi, Yokohama, JA;
Yutaka Fukushima, Yokohama, JA;
Assignee:
Hitachi, Ltd., , JA;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H04B / ;
U.S. Cl.
CPC ...
1791 / ; 179 / ;
Abstract
A testing system for testing an impedance of a subscriber line by connecting a test circuit to the subscriber line through one of channels in a network including current self-holding semiconductor switching devices, wherein a series circuit of a second channel and a constant current source is connected in parallel with said first-mentioned channel whereby the current self-holding semiconductor switching devices in said first and second channels are kept conductive by said constant current source.