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. 19, 1988
Filed:
Dec. 22, 1986
Regis B Mellon, Mulberry, FL (US);
Protel, Inc., Lakeland, FL (US);
Abstract
A toll telephone coupled to tip and ring conductors of a toll trunk and through which various toll signals flow between a central office and the telephone (such as a coin ground signal to indicate the presence of the coin) has a hook switch with an off-hook condition for instituting the flow of loop current. To allow local, coin-free calls, the telephone has electronic circuitry for applying a simulated coin ground signal to the tip conductor continuously during the off-hook condition to permit coin-free calls to be made from the toll telephone. Additionally, the telephone includes a single relay system for providing an open-loop coin check responsive to a corresponding signal from the central office. The telephone provides a notch filter for discriminating against one of the multiple frequencies of a bong tone, thus allowing the remaining frequency to be detected.