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. 02, 1988
Filed:
Jun. 24, 1985
Rolf G Meier, Nepean, CA;
John A Barsellotti, Kanata, CA;
Mitel Corporation, Kanata, CA;
Abstract
A constant current line circuit for connection to balanced tip and ring leads of a telephone line and unbalanced transmit and receive leads of a PABX. A differential amplifier receives and applies incoming audio signals carried by the tip and ring leads to the unbalanced transmit lead, and detects D.C. loop current flowing through the tip and ring leads and generates a D.C. signal in response thereto. A voltage controlled feed current supply, connected in a circuit to the differential amplifier, generates a constant current D.C. voltage to the tip and ring leads in response to receiving the D.C. signal, and an integrator circuit is connected in a feedback path from the output of the differential amplifier to a voltage control input of the supply, for filtering audio signals received by the differential amplifier and regulating the generated D.C. signal to a quiescent value of approximately zero volts. The line circuit provides simultaneous bidirectional signal translation and constant D.C. feed current generation in response to detecting the D.C. loop current and generating and regulating the D.C. signal.