Signal matching signal substitution
First Claim
1. A signal matching signal substitution system wherein substitute signals in a substitute channel are substituted at a viewer'"'"'s television receiver in lieu of normal signals in a normal channel, said system comprising receiving means for selectively receiving signals in respective normal and substitute television channels, input gain control means responsive to a gain control signal for controlling the output signal level of said receiving means, means for switching said receiving means between said normal channel and said substitue channel, means for determining the input signal level of currently received signals in a currently received channel and generating an amplitude signal indicative of said input signal level, set point means responsive to said amplitude signal corresponding to the input signal level for the normal channel most recently received for providing a set point for said output signal level, and means responsive to said set point and said output signal level for generating said gain control signal maintaining said output signal level at said set point.
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Accused Products
Abstract
A signal matching signal substitution system includes a tuner for selectively receiving signals in respective television channels with an input gain control for controlling the signal output level of the tuner. The system substitutes television signals in a substitute channel in lieu of normal signals in a normal channel selected by a viewer. The system has a component for determining the input signal level of currently received signals in a currently received channel and generating a current amplitude signal. A set point generator is responsive to the current amplitude signal corresponding to the normal channel most currently received for providing a set point for the output signal level. A gain control signal generator is responsive to the set point and the signal output level for generating a gain control signal maintaining the output level at the set point. The set point may be set at a predetermined fixed level when the current amplitude signal corresponding to the most current normal channel is relatively high and is set at progressively lower levels when the current amplitude signal corresponding to the most current normal channel is below a transition level. The set point at the progressively lower levels is noise limited to provide substantially equal signal to noise ratios in the signal output of the tuner in both the normal and the substitute channels upon signal substitution. The set point is gain limited to the maximum signal output achievable by the gain control for the normal channel.
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Citations
8 Claims
- 1. A signal matching signal substitution system wherein substitute signals in a substitute channel are substituted at a viewer'"'"'s television receiver in lieu of normal signals in a normal channel, said system comprising receiving means for selectively receiving signals in respective normal and substitute television channels, input gain control means responsive to a gain control signal for controlling the output signal level of said receiving means, means for switching said receiving means between said normal channel and said substitue channel, means for determining the input signal level of currently received signals in a currently received channel and generating an amplitude signal indicative of said input signal level, set point means responsive to said amplitude signal corresponding to the input signal level for the normal channel most recently received for providing a set point for said output signal level, and means responsive to said set point and said output signal level for generating said gain control signal maintaining said output signal level at said set point.
Specification