This analog volt-ammeter was found in an Electronics World of 1968. It makes use of a 0-1 mA analog milliammeter. Accuracy depends on the components.
This circuit is from a Popular Electronics from the 90s. The integrated circuit admits equivalents...
This very interesting project was obtained in a 1980 publication. It consists of a device that is...
This circuit beeps when the sensor is triggered by the opening of the freezer door or other...