Emergency locating transmitter and receiver system
First Claim
1. A receiver for receiving radio frequency transmissions intercepted by an antenna comprising:
- radio frequency means for selecting and amplifying the radio frequency transmissions intercepted by said antenna;
intermediate frequency means for converting the selected and amplified radio frequency transmissions to a lower, intermediate frequency signal;
phaselock loop means for locking onto an unmodulated portion of the intermediate frequency signal for the duration of said unmodulated portion;
means for measuring the duration of said phaselock loop means being locked, and then unlocked immediately after being locked;
comparator means for detecting a match between the measured duration of said phaselock loop means being locked and a first set of values stored in said comparator means, and for detecting a match between the measured duration of said phaselock loop means being unlocked immediately after being locked and a second set of values stored in said comparator means, wherein different pairs of values from the two sets correspond to different items of information; and
means for indicating that a pair of measured durations of said phaselock loop means being locked and unlocked immediately after being locked corresponds to a particular pair of values stored in said comparator means.
1 Assignment
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Accused Products
Abstract
A receiver and transmitter are provided for a distress incident locating telecommunications system. The receiver is a superheterodyne AM receiver which applies the received distress transmissions to a normally unlocked phaselock loop which locks onto the unmodulated carrier signal portion of the distress transmission. The duration of the phaselock loop being locked, and unlocked immediately after being locked, are measured and compared to predetermined values to find a match. Each of the predetermined values corresponds to an item of information, and if a match is found, the receiver indicates it. The receiver is also capable of extracting audio information present in the distress transmission. The transmitter generates three signals which can be applied to a transmitting antenna. These signals are a radio frequency carrier signal, and a carrier signal modulated by a distress waveform or by an audio signal. The signal which is ultimately applied to the transmitting antenna will have four parameters where each set of parameters corresponds to a different item of information. The parameters are which one or more of the three signals will be applied to the antenna, the sequence of application of the signals to the antenna, the duration of each of the signals, and the frequency of the audio signal.
16 Citations
7 Claims
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1. A receiver for receiving radio frequency transmissions intercepted by an antenna comprising:
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radio frequency means for selecting and amplifying the radio frequency transmissions intercepted by said antenna; intermediate frequency means for converting the selected and amplified radio frequency transmissions to a lower, intermediate frequency signal; phaselock loop means for locking onto an unmodulated portion of the intermediate frequency signal for the duration of said unmodulated portion; means for measuring the duration of said phaselock loop means being locked, and then unlocked immediately after being locked; comparator means for detecting a match between the measured duration of said phaselock loop means being locked and a first set of values stored in said comparator means, and for detecting a match between the measured duration of said phaselock loop means being unlocked immediately after being locked and a second set of values stored in said comparator means, wherein different pairs of values from the two sets correspond to different items of information; and means for indicating that a pair of measured durations of said phaselock loop means being locked and unlocked immediately after being locked corresponds to a particular pair of values stored in said comparator means. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification