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 is the single-sourced version of the previous oscillator. Frequency can be changed by...
This is a commercial circuit found in Radio Electronics magazine from September 1960. The circuit has...
This circuit is from a 1998 Poptronics. The circuit triggers a buzzer after a certain time, waking...