This circuit appeared in the 1991 Electronics Experimenter Handbook. The circuit is for remote controls of the time that are slower than today's and may not work with modern types.
This circuit can function as a light alarm by changing the sound when light falls on the sensor....
Based on a unijunction transistor, this circuit was found in the January 1994 issue of Electronics Now...
Although it is a common configuration today, these circuits were taken from an old publication. The...