This circuit was found in RCA documentation from the 1960s. The circuit uses components from that time and can measure speeds up to 10,000 rpm.
This circuit activates a relay when the water reaches the sensors. The circuit is from a magazine...
The noise comes from the PN junction of a common silicon diode. Since no gain is given by the...
We have here an interesting audio preamplifier, which can be useful to those who are looking to...