This commercial radio with 3 earphone listening transistors was manufactured in Japan in the 1960s. The medium-wave circuit uses germanium transistors and is powered by a 9 V battery.
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...