Despite being from a 1969 publication, the transistors used have current equivalents such as BC548 and BC558. The circuit generates signals from 1 500 to 20 000 Hz and 4 scales.
This circuit can be used to recognize a tone by its frequency. When this tone is present in a...
This simple SCR delay circuit for activating a relay was found in documentation from the 1980s. The...
This flasher or neon signal powered by batteries was found in old documentation. The transformer must...