In the figure we have a stereo decoder from the 70's with pilot lamp for signal indication. The circuit employs a component of the time, which is uncommon today.
This circuit is from September 1984 Radio Electronics. The frequency can be changed by changing C1 and...
This optical coupler for short distances is powered by 12 V which is the voltage of the lamp and...
This circuit was found in a 1980s Intersil documentation. The integrated circuit used is not...