Two-tone solar buzzer (CB20493E)

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

Stereo FM Transmitter (CB16538E)
This small FM transmitter for short distances has a stereo multiplexer and can be used over an...
Headset Amplifier H530 (CB18399E)
This commercial circuit of 3 transistors was found in Japanese documentation from the 1960s. The...
Wien Bridge Oscillator MC3403 (CB15293E)
We found this circuit on Motorola's 1993 Linear Interface ICs. Equivalent operational amplifiers can be...