This circuit is from American documentation from the 70s. The circuit makes use of the operating system of the time, but it can be implemented with more modern equivalents.
Found in an old publication, this is a transmitter with a spark coil. The high frequency...
This circuit was found in a 90s Hands-On Electronics. When a signal appears at the headphone...
In the figure we give a suggestion of a high-power stage to excite a speaker with the 2N3055. The...