发明名称 |
Trunked radio monitoring system |
摘要 |
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. When a first bit pattern is detected in a digital message, subsequently transmitted data is stored. Information is extracted from the stored data to obtain a channel assignment code indicating a frequency over which communications take place and a talk group identification code identifying a talk group in the trunked communication system participating in a communication. 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 successfully 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 received by the control channel receiver.
|
申请公布号 |
US5956648(A) |
申请公布日期 |
1999.09.21 |
申请号 |
US19970820338 |
申请日期 |
1997.03.12 |
申请人 |
G/TRACKER TECHNOLOGIES LLC |
发明人 |
BRENNAN, TERENCE;SULLIVAN, TERENCE SEAN |
分类号 |
H04W24/00;(IPC1-7):H04Q7/00 |
主分类号 |
H04W24/00 |
代理机构 |
|
代理人 |
|
主权项 |
|
地址 |
|