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 simple oscillator with just one transistor has a frequency determined by the characteristics of the...
This Zero Crossing Detector was found in a 1972 RCA manual, but it can be made using any modern...
The circuit shown was found in a Japanese publication from the 1960s. Transistors can be...