Multiplexed television signal processing system
First Claim
1. A multiplexed television signal processing system comprising:
- a receiving circuit for receiving a binary signal transmitted in superposition on a television signal;
a reference voltage generating circuit for generating a first reference voltage, a second reference voltage higher than said first reference voltage and a third reference voltage lower than said first reference voltage by a difference between said first reference voltage and said second reference voltage;
a variable gain amplifier circuit adapted to receive said television signal having the binary signal superimposed thereon;
a clamp circuit for clamping and holding a lower (or upper) level of a pilot signal in said binary signal to said third (or second) reference voltage during a period around the pilot signal period;
a control circuit for detecting the upper (or lower) level of said pilot signal during the period around the pilot signal period, comparing the detected level with said second (or third) reference voltage and controlling the gain of said variable gain amplifier such that said detected level becomes equal to said second (or third) reference voltage; and
an amplitude discrimination circuit for amplitude-discriminating said binary signal using said first reference voltage as a discrimination reference.
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Abstract
A signal processing system in a transmission system like Teletext System in which a binary signal is superimposed on a television signal for transmission is disclosed. When the binary signal is received, an upper (or lower) level of a pilot signal in the binary signal is clamped to a first reference voltage by a clamp circuit while the amplitude of the pilot signal is controlled by a variable gain amplifier such that the lower (or upper) level of the pilot signal becomes equal to a third reference level. The binary signal is then amplitude-discriminated using a second reference voltage as a discrimination reference. In this manner, the binary signal is correctly converted to a digital signal.
102 Citations
5 Claims
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1. A multiplexed television signal processing system comprising:
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a receiving circuit for receiving a binary signal transmitted in superposition on a television signal; a reference voltage generating circuit for generating a first reference voltage, a second reference voltage higher than said first reference voltage and a third reference voltage lower than said first reference voltage by a difference between said first reference voltage and said second reference voltage; a variable gain amplifier circuit adapted to receive said television signal having the binary signal superimposed thereon; a clamp circuit for clamping and holding a lower (or upper) level of a pilot signal in said binary signal to said third (or second) reference voltage during a period around the pilot signal period; a control circuit for detecting the upper (or lower) level of said pilot signal during the period around the pilot signal period, comparing the detected level with said second (or third) reference voltage and controlling the gain of said variable gain amplifier such that said detected level becomes equal to said second (or third) reference voltage; and an amplitude discrimination circuit for amplitude-discriminating said binary signal using said first reference voltage as a discrimination reference. - View Dependent Claims (2, 3, 4, 5)
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Specification