Door buzzer or alarm (CB20492E)

This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose NPN.

Varicap Variable Frequency Oscillator (CB4587E)
The great advantage of the circuit shown in the figure is that its frequency is controlled by a...
Electronic Dice with the 4018 (CB4630E)
A recreational application of the 4018 is shown in the figure in which we have electronic dice....
Solar metronome (CB20499E)
This ultra-low power metronome was found in a 1991 documentation. The output transistor is general...