Teletext reception indicator
First Claim
Patent Images
1. For use with a teletext decoder which decodes teletext signals having a framing code, a teletext indicator, comprising:
- control means associated with the teletext decoder and responsive to the decoder'"'"'s detection of a framing code for generating a control signal, said control means being responsive to vertical rate gate pulses for resetting the control signal; and
indicating means responsive to the control signal for indicating the receipt of a valid teletext signal.
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Abstract
An indicator is described for alerting a television viewer to the fact that a teletext signal is being received. In the preferred embodiment, the indicator includes a control which senses the detection of the framing code associated with the received teletext signal to actuate an indicator lamp.
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Citations
7 Claims
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1. For use with a teletext decoder which decodes teletext signals having a framing code, a teletext indicator, comprising:
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control means associated with the teletext decoder and responsive to the decoder'"'"'s detection of a framing code for generating a control signal, said control means being responsive to vertical rate gate pulses for resetting the control signal; and indicating means responsive to the control signal for indicating the receipt of a valid teletext signal. - View Dependent Claims (2, 3, 4)
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5. For use with a teletext decoder which decodes teletext signals having a framing code, a teletext indicator comprising:
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control means comprising first counting means responsive to the detection of N framing codes by the teletext decoder for initiating a control signal and second counting means responsive to N vertical rate gate pulses developed immediately following the generation of a control signal for resetting the control signal; and indicating means responsive to the control signal for indicating the receipt of a valid teletext signal.
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6. For use with a teletext decoder which decodes teletext signals having a framing code, a teletext indicator, comprising:
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a gate for sensing the decoder'"'"'s detection of a framing code; means for applying to said gate a window enable signal which occurs concurrently with a valid framing code, thereby to provide a first output signal corresponding to a windowed framing code; a first flip-flop responsive to said first output signal for developing a control signal; means for resetting the flip-flop at a vertical rate; and means responsive to the control signal for indicating the receipt of a valid teletext signal.
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7. For use with a teletext decoder which decodes teletext signals having a framing code, a teletext indicator comprising:
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a gate for sensing the decoder'"'"'s detection of a framing code; means for applying to said gate a window enable signal which occurs concurrently with a valid framing code, thereby to provide a first output signal corresponding to a windowed framing code; a first flip-flop responsive to said first output signal for developing a first control signal; means for developing a vertical rate gate signal; means for resetting said first flip-flop at a vertical rate in response to said vertical rate gate signal; first counting means responsive to the development of N first control signals for developing a second output signal; a second flip-flop responsive to said second output signal for developing a second control signal; second counting means enabled by said second control signal for counting N vertical rate gate signals for developing a reset control signal coupled for resetting said second flip-flop; and means responsive to the second control signal for indicating the receipt of a valid teletext signal.
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Specification