Two-tone solar buzzer (CB20493E)

This circuit was found in a 1991 publication. The transistor can be a general-purpose type.

Wien Bridge Sine Oscillator (CB12738E)
The figure shows a Wien Bridge circuit with non-linear feedback. The resistance of the RL lamp is...
Commercial Radio TR 62 (CB18370E)
This commercial medium and short-wave radio was manufactured in Japan in the 60s. The circuit has...
Self-Powered MW Receiver (CB11528E)
The energy that powers this radio's amplifier circuit is obtained from the signal itself. The coil...