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:
Oct. 09, 1979
Filed:
Feb. 17, 1978
Tom L Blackburn, San Jose, CA (US);
GTE Automatic Electric Laboratories, Incorporated, Northlake, IL (US);
Abstract
A first network can be switched into and out of connection with a lowpass filter disposed at one of the two opposite carrier terminal ends of a loop transmission path employing a double-sideband carrier. When the filter and network are so connected, an oscillator producing a first test signal of selected frequency and amplitude is formed. This signal modulates the carrier wave generated by the existing carrier oscillator at this terminal end. The modulated signal passes along the path to the opposite terminal end where it is demodulated and detected. The detector threshold is set so that the detector responds to the demodulated first test signal, but does not respond to normal voice and other test signals. The detected demodulated signal energizes the station carrier oscillator at the opposite end whereby its carrier wave is modulated. The resultant second modulated test signal passes back along the path to the original terminal where it is demodulated, and the presence of the carrier is detected. The amplitude of the demodulated signal also may be measured and compared to that of the original test signal to establish the loss in the transmission path.