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:
Aug. 19, 1980
Filed:
Jan. 29, 1979
Harry R Rasmussen, Tacoma, WA (US);
Gene A Kimzey, Puyallup, WA (US);
Crest Industries, Inc., Puyallup, WA (US);
Abstract
The exclusion circuit disclosed herein provides for line privacy in a key telephone system of the type in which a control unit provided at each of a plurality of stations can be operated to selectively connect one or more telephone lines to the phone set at the corresponding station. Within each control unit, an exclusion circuit is provided for each telephone line that extends to the control unit, and is connected so as to cooperate with a line condition sensing circuit, a line switching relay, a relay latching circuit and a manually operated line selector switch, all of which are associated with the same line as the exclusion circuit. When the telephone line is in an idle condition or a hold condition, the exclusion circuit is in a nonexclusion, quiescent mode during which the manually operated selector switch is effective to switch the line relay and, in conjunction with the line condition sensing circuit, cause the relay latching circuit to latch the line relay in a condition that connects the telephone line to the station set for so long as the telephone line remains busy (in an off-hook condition). To prevent other stations from coming onto a busy line the exclusion circuits associated with the same telephone line, but located at the other stations, respond to the busy condition on the line, as detected by the associated sensing circuits, and after a predetermined delay interval such other exclusion circuits assume an exclusion mode in which the associated line selector switches are no longer effective to operate the corresponding line relays. The phone stations, other than the station that initially picks up the telephone line, are thus unable to connect the associated phone sets to the line. When the line becomes idle or is placed on hold, and either of those conditions are detected by the sensing circuits at the various stations, the associated exclusion circuits are restored to their quiescent mode, enabling any one of the stations to pick up the line.