This circuit is from an old Signetics documentation. It can be implemented with modern operational amplifiers. The power supply must be symmetrical.
In the figure we have the way to use a stepper motor as an encoder. Operational amplifiers can be of...
Found in 90’s English documentation, this rising and falling siren, manually activated, drives a...
The sensor of this circuit is an NTC with a resistance between 200 and 1000 ohms. The resistor R1 must...