This circuit was found in an Electronic Design from the 90s. The circuit uses a type J thermocouple that can measure from -50 to + 100º C. Power is provided by a 3 V lithium battery.
The sound produced by this circuit, from a 1978 publication, depends on the humidity between the...
In a September 1992 Radio Electronics article, we found this basic 555 circuit used to generate fixed...
This circuit is suggested by Motorola, using a 4N26 type coupler and an MC1733 type operational....