This circuit has the intensity of the signals controlled by the light that falls on the sensor. Note that it is not a frequency-controlled oscillator. Equivalent transistors can be used.
We found this circuit in an Electronics Handbook from the 1980s. It filters out noise from a radio...
We found this circuit in the May 1989 issue of Radio Electronics magazine. The circuit uses...
This TTL circuit generates a 100 MHz signal for digital instruments. The CI is not easy to obtain,...