The integrated circuit used in this amplifier is uncommon today, since the project is from the 90s. The power is 24 V, and the gain of the circuit is 40dB. The input resistance is 1 M ohms.
This LED indicator circuit uses an LM339 comparator. The circuit was found in the January 1995...
This circuit is from an 80's documentation. Equivalent transistors can be used. The circuit is...
We found this circuit in a 1967’s Electronics World. The circuit can be made with modern...