H - Electricity – 04 – B
Patent
H - Electricity
04
B
325/27
H04B 7/00 (2006.01) G01S 1/68 (2006.01)
Patent
CA 1281379
Abstract of the Disclosure A telecommunications system having a transmitting antenna and a transmitter for generating a radio frequency carrier signal to be applied to the antenna. An audio signal is generated as well as a series of rectangular pulses having a constant duty cycle whose pulse repetition rate is controllable to cyclically vary between a set of limits. The radio frequency carrier signal is modulated with an audio signal for one period and with the series of rectangular pulses for another period. A receiving antenna is provided for intercepting the radio frequency signal radiated by the transmitting antenna. The intercepted signal is amplified by -the receiving antenna and the amplified signal is converted to a lower intermediate frequency signal. A phaselock loop is provided for locking onto an unmodulated portion of the intermediate frequency signal for the duration of the unmodulated portion. A measuring circuit measures the duration of the phaselock loop being locked, and then unlocked immediately after being locked. A comparator detects a match between the measured duration of the phaselock loop being locked and a first set of values stored in the comparator, and for detecting a match between the measured duration of the phaselock loop being unlocked immediately after being locked and a second set of values is stored in the comparator, wherein different pairs of values from the two sets correspond to different items of information. An indicator device indicates that a pair of measured durations of the phaselock loop being locked and unlocked immediately after being locked corresponds to a particular pair of values stored in the comparator.
615553
National Aeronautics And Space Administration
Swabey Ogilvy Renault
Wren Paul E.
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