In the figure we have the way to implement a NO OR or NOR gate with an operational amplifier. The number of inputs can be changed.
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...