Found in a Popular Electronics from the 1990s, this circuit monitors the voltage of a power supply or battery. The trigger voltage is adjusted with a potentiometer.
CMOS 4046 (PLL) is not very common. In this circuit it generates short pulses to excite a high...
The sensor of this circuit is an NTC of 20 to 50 k resistance at room temperature. The circuit is from a...
This circuit was found in an English documentation from 1969. The transistors are of the time,...