This simple three-LED sensor uses an NTC at the input. The circuit is based on an uncommon integrated component today. We found it in documentation from the 80s.
This circuit using an operational amplifier was found in old American documentation. It can be...
This is a voltmeter with high input resistance. The transistor is germanium. We found it in an...
Two NAND gates are used in the configuration shown here to perform as a monostable triggered by...