This circuit was found in a Popular Electronics of the 1990s. The sensor is a rotating mechanical system with a propeller-driven magnet to count pulses with a reedswitch.
This oscillator, which can be used as a signal injector, was found in a Popular Electronics from the 90s....
This high-gain digital amplifier uses general-purpose transistors. The supply voltage is logic...
With this circuit of a Popular Electronics from the 90's it is possible to test a diode with the...