This circuit of starting lights for auto-race was found in an English documentation from the 80's. The LEDs must be of different colors, for greater realism.
This encoded lock circuit with alarm for use in homes was found in a publication from the 90s. The...
The circuit shown was found in the 1994 National Semiconductor Linear Applications Handbook. The...
This circuit is from a 1979 documentation. The FET can be the BF245 or MPF102 and the bipolar...