This variable frequency circuit was found in a Popular Electronics from the 90s. The circuit outputs to a small speaker and can be powered by voltages as low as 3 V.
Found in a 1968 American documentation, this circuit generates sawtooth signals whose rise and...
This TTL siren is formed by two oscillators using each two Gates of a 7400. Frequency or the...
Although it is a circuit from the 80s, it can still be easily implemented today because the...