The circuit is from the MC1539 manual, an operational one close to the 741. The transistor admits equivalent and must be mounted in a good heat sink.
Found in Popular Electronics from the 90s, this circuit uses a reed switch on the rails as a...
This low input impedance amplifier stage was found in a 1963 documentation. The circuit employs a...
This 2003 circuit uses two types of sensors: by reed-switch and by infrared. If the magnetic...