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. 11, 2003
Filed:
Sep. 20, 1999
Terence Brennan, Florence, MA (US);
Terence Sean Sullivan, Melrose, MA (US);
Other;
Abstract
A method and apparatus for passively monitoring communications in a trunked communication system. Digital messages transmitted over a control channel at a particular frequency are monitored with a receiver. Transmitted communication signals are demodulated and stored. The stored signals are tested to identify messages and to extract talk group and channel assignment codes. If the talk group is a talk group of interest, the receiver is tuned to the frequency corresponding to the channel assignment code so that voice communications are monitored. The receiver is tuned to the control channel after each voice communication so that a communication including multiple transmissions on different frequencies is coherently monitored by retuning the receiver in accordance with the received channel assignment codes. In an alternative embodiment, separate receivers are provided for the control channel and for voice communications. The voice receiver is continually tuned to different working channels in response to talk group and channel assignment codes extracted from stored information received by the control channel receiver.