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 uses an unusual electromechanical component: a mechanical blade resonator. The...
This circuit from a Japanese publication in 1968 uses germanium transistors from the time like the...
Found in a 90s Electronic Design, this circuit can provide a relatively high-power output. The basic...