Found in a Popular Electronics from the 90's, this circuit is used to indicate the operation of telephones of the time. The circuit is TTL.
This circuit appears elsewhere on the site. The circuit shown is from an American 1980s...
This circuit can produce signals up to 100 kHz depending on C1 and R1 adjustment. The output has a...
This circuit is from an old publication from 1977 and can be implemented with more modern...