Two-tone solar buzzer (CB20493E)

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

Symmetrical Adjustable Source (CB16785E)
This symmetrical 1.2 to 35 V source was found in a 1994 documentation. The integrated circuits are...
4-channel mixer (CB8756E)
Found in a 90s Elektor, this mixer makes use of integrated circuits of the time. The supply must be...
1 to 5 W amplifier TDA1011 (CB15975E)
This amplifier is specifically designed for portable radio and recorders with a 4 ohms load....