This circuit was obtained from Dutch documentation from 1964. The components are of the time, but current equivalents such as BC548 to BC108 can be used.
In the figure we have the simple way of controlling a load or having a signal from an optical...
This circuit was found in a 90s Popular Electronics. It uses an LS3404 melody chip that has...
The integrated circuit used in this application is the National Semiconductor's LM2907, the...