Guard tone capture method
First Claim
1. A decoder for receiving and decoding a series of coded messages wherein a first amplitude of a particular frequency ends a first coded message and a second amplitude of said particular frequency begins a second coded message, said decoder comprising,receiver means for receiving said coded message,detector means responsive to said receiver means for detecting said particular frequency, said detector means having at least first and second states, wherein said detector means can detect said first and second amplitudes of said particular frequency in said first state and said second amplitude of said particular frequency in said second state,sensor means responsive to said receiver means for detecting a threshold amplitude of said coded message,control means responsive to said detector means and said sensor means to control the state of said detector means,function means response to said receiver means and enabled by said control means,said control means being responsive to detection of said first amplitude of said particular frequency by said detector means to hold said function means in an enabled condition, said control means also being responsive to detection of a threshold amplitude by said sensor means to change said detector means from said first state to said second state thus allowing said detector means to detect said second amplitude of said particular frequency, said control means disabling said function means in response to a detection of said second amplitude of said particular frequency by said detector means in said second state.
1 Assignment
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Accused Products
Abstract
A decoder for receiving and decoding a coded signal includes a particular frequency fo with a first and second amplitude. The first amplitude of the frequency fo is associated with the end of a first coded message while the second amplitude of the frequency fo is associated with the beginning of a second coded message. The decoder includes a receiver for receiving the coded signal, a tone detector circuit for detecting the frequency fo, a level sensor responsive to the receiver output, a function block for performing a command and a control unit responsive to the tone detector circuit and the sensor means. The tone detector and control unit operate in one of at least two possible states. In the first state the control unit causes the tone detector to respond to the first amplitude of the frequency fo. When the level sensor senses the second amplitude of the frequency fo the control unit responds by placing the tone detector circuit into its second state. In its second state, the tone detector circuit detects whether the level sensor was tripped by the frequency fo or by some other frequency. If the tone detector circuit detects the frequency fo, the control unit causes the decoder to end its decoding of the first message and begin the decoding of a second message. If the tone detector circuit in its second state fails to detect the frequency fo, the control unit returns the tone detector circuit to its first state so it may continue to decode the first amplitude of the frequency fo associated with the first coded message.
24 Citations
14 Claims
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1. A decoder for receiving and decoding a series of coded messages wherein a first amplitude of a particular frequency ends a first coded message and a second amplitude of said particular frequency begins a second coded message, said decoder comprising,
receiver means for receiving said coded message, detector means responsive to said receiver means for detecting said particular frequency, said detector means having at least first and second states, wherein said detector means can detect said first and second amplitudes of said particular frequency in said first state and said second amplitude of said particular frequency in said second state, sensor means responsive to said receiver means for detecting a threshold amplitude of said coded message, control means responsive to said detector means and said sensor means to control the state of said detector means, function means response to said receiver means and enabled by said control means, said control means being responsive to detection of said first amplitude of said particular frequency by said detector means to hold said function means in an enabled condition, said control means also being responsive to detection of a threshold amplitude by said sensor means to change said detector means from said first state to said second state thus allowing said detector means to detect said second amplitude of said particular frequency, said control means disabling said function means in response to a detection of said second amplitude of said particular frequency by said detector means in said second state.
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9. A method for detecting and decoding a coded signal including first and second messages, wherein a first amplitude of a first frequency is associated with a first coded message, and a second amplitude of said first frequency is associated with a second coded message, said method comprising the steps of,
a. decoding a first amplitude of a first frequency of said first message, while simultaneously monitoring the amplitude of said coded signal, b. detecting the crossing of a threshold amplitude by said coded signal, c. determining if the frequency of the portion of said coded signal crossing said threshold amplitude is equal to said first frequency, d. decoding said second message if step (c) determination is positive, and e. returning to decoding a first amplitude of a first frequency of said first message if the step (c) determination is negative.
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12. A decoder for receiving and decoding a series of coded messages from a remote terminal wherein a first amplitude of a first frequency is associated with a first coded message and a second amplitude of a first frequency followed by a second frequency is associated with second coded message, said decoder comprising;
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a receiver means for receiving said series of coded messages, frequency detection means responsive to said receiver means to detect said first and second amplitudes of said first frequency and said second frequency, control means responsive to said frequency detection means detection of said first and second amplitudes of said first frequency, function means enabled and disabled by said control means, said control means holding said function means in an enabled condition in response to detection of said first amplitude of said first frequency by said frequency detection means, said control means responding to the simultaneous detection of said first and second amplitude of said first frequency by said frequency detection means to become responsive to detection of said second frequency by said frequency detection means, said control means disabling said function means in response to detection of said second frequency by said frequency detection means. - View Dependent Claims (13, 14)
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Specification