The components used in this National Semiconductor circuit are not common today, but the configuration can be adapted to use more modern components.
This circuit was obtained in a 1977 technical documentation. The sensor is a thermistor from 10k...
This is a Japanese commercial radio from the 60s. The superheterodyne circuit of 7 transistors for medium...
This unusual circuit from a Popular Electronics of the 90s uses LED indicators, operating as a...