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:
Jul. 04, 1978
Filed:
Oct. 20, 1977
Ralph R Roge, Clarendon Hills, IL (US);
Paul J Curtis, Woodridge, IL (US);
Wescom, Inc., Downers Grove, IL (US);
Abstract
A ground start loop current detector is used to monitor the loop current in a telephone subscriber loop when the subscriber requests service by grounding one line of the loop (ground start), when a busy subscriber discontinues use by opening the loop, and when a called subscriber answers in response to ringing by closing the loop. In order to operate in the presence of longitudinal (common mode) interference currents in the loop, especially in the ground start situation where only one line is monitored, the detector incorporates a differential amplifier which has its inputs connected to the loop through transformer windings that are phased so as to equalize the effects of longitudinal currents on the inputs of the differential amplifier.