| 摘要 |
An automatic tuning system for television receivers. An auxiliary frequency is first connected losely to the high point of the band-pass filter while the amplification stage is completely turned off. After optimum tuning of the band-pass filter, the auxiliary frequency is turned off and when the pre-amplifier is fully turned on the input circuit is tuned. The frequency of the tuner oscillator is at the same time raised by half the amount of the second tone intermediate frequency. The tone carrier of the channel selected now serves as an auxiliary frequency. After tuning the tuner oscillator frequency is again switched to the desired value, whereby the input circuit is tuned to mid-band frequency, since the tuning voltage is lowered by the same amount as for adjustment of the desired oscillator frequency. |
