Importance

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Abstract

In a phase locked loop (PLL) tuning system for a television receiver, the capability of tuning channels with RF signals with non-standard frequencies arbitrarily near the respective standard frequencies is provided by making a frequency divider used in the PLL for establishing the frequency relationship of the local oscillator signal to the crystal oscillator signal controllable in a limited range corresponding to a frequency range less than the frequency separation between channels. As one feature of this system the divider is controlled in accordance with predetermined AFT signal conditions. As another feature, the division factor of the divider is initially offset from its nominal value corresponding to the standard frequency for the selected channel and thereafter the frequency of the local oscillator signal is controlled in response to the AFT signal.

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First Claim