Two-tone solar buzzer (CB20493E)

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

Tone Control Mixer (CB4918E)
The integrated circuit used in this 80's mixer is the LM301A. However the circuit can be used to...
Cascading the 4520 (CB083E)
For counting to values higher than 16, many 4520 can be cascaded as shown in Figure . The EN...
Voltage divider with zeners (CB4242E)
I found this simple zener diodes voltage divider circuit in an old documentation. The resistor...