Through the TTL output this circuit can be used as a shield. The sensor is a platinum probe, and the operational amplifier can be replaced by a modern equivalent, preferably of low voltage.
This circuit was obtained in a 1960 transistor manual from Sylvania. The circuit can be...
This circuit is one of many similar ones that can be found on this site. This version is from...
The transistors on this circuit can be 2N2222. The circuit is from American documentation from the...