Micro siren (CB21234E)

This circuit with the LM3909 can be powered with voltages from 3 to 5 V. We found it in a Popular Electronics from the 90s.

Frequency Doubler with the 741 (CB12267E)
In the figure we have a circuit with two operational amplifiers 741 capable of doubling the...
Shield for relay activation in Motor control (CB23716E)
What differentiates this circuit from the previous one is the need for a much smaller current to...
Microprocessor supervisor (CB9321E)
This circuit was obtained in a Maxim documentation from the 90's. The circuit applies to...