For measurements between 30 and 40º C this circuit was found in the documentation of 1968. The sensor is a difficult component to obtain today.
Found in the July 1968 Supertena Bulletin of a Popular Electronics, this receiver makes use of the...
This switching source was obtained in a 1976 National Semiconductor manual. For the indicated...
This configuration appears several times on this site. The circuit can generate a 100 kHz or other...