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:
Mar. 29, 1988
Filed:
Nov. 14, 1985
Applicant:
Inventors:
Assignees:
Nitsuko Limited, Tokyo, JP;
Nippon Telegraph and Telephone Corporation, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H04M / ;
U.S. Cl.
CPC ...
379253 ; 379418 ;
Abstract
A circuit for sending out a ringing signal of a high voltage and a low frequency to a telephone set through a telephone line repeatedly with a predetermined time interval. In order to omit use of a high power oscillator and relays, a D.C. power supply of a high voltage is operatively connected to the telephone line through phototransistors of photocouplers being driven by a pulse signal having a low voltage and the low frequency under control of pulses occurring at the predetermined time intervals so that the ringing signal is sent out to the telephone set repeatedly with the predetermined time interval.