Importance

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Abstract

A circuit is described for maintaining an input signal to a limiter used to limit amplitude excursions of a signal to be angle demodulated. Means are provided for detecting a temporary loss in signal to said limiter resulting from the loss of signal due to large negative amplitude modulation or other factors. When the amplitude of the angle modulated wave falls below a predetermined minimum, a substitute intermediate frequency signal is generated to maintain the limiter in a limiting condition during the temporary loss in broadcast signal. The substitute intermediate frequency signal has a frequency substantially equivalent to the intermediate frequency signal developed from the broadcast signal during periods when the amplitude of the broadcast signal is adequate. The substitute signal prevents the occurrence of noise generated from an angle demodulator due to a temporary loss in signal.

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First Claim