Amplifier for voltage reference (CB9009E)

Found in American documentation from the 1980s, this circuit applies to modern operational amplifiers. The circuit has offset adjustment.

Variable Voltage Controlled Attenuator (CB4236E)
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...
Harmonic generator (CB9454E)
Found in a 90s Electronic Design, this circuit generates harmonics from a sinusoidal input signal....
Water alarm with lock (CB6957E)
Published in an old Popular Electronics, this circuit makes use of components that are still...