This circuit was obtained in a Hands-On Electronics from the 90's. The circuit turns on one LED at the end of the timer, erasing the other. The timing can be increased by changing C1.
August 2016 - It can be obtained from Mouser Electronics, Modules Intel Curie low power containing...
This circuit was found in a 1965’s General Electric documentation. It is intended for low voltage...
This transformerless 16-ohm speaker circuit was found in a Radio Electronics from October 1963. The...