This circuit is from a 60's documentation. The capacitance C1 can be between 20 pF and 0.01 uF depending on the generated frequency. Equivalent transistors may be employed.
With this luminous remote control, which we found in a 1990 publication, using a flashlight you...
We found this circuit in a 1967 Electronics World. The circuit can be designed to control other...
This circuit can be used in a signal level indicator with LEDs. The circuit is from an Electronics Now...