Found in Radio Electronics from the 90s, this circuit is based on the 555 directly feeding a small tweeter. An amplifier stage can be added.
This high quality circuit with complementary symmetry was found in an Electronics World of 1966....
This circuit was obtained from an American documentation from the 1980s. The T1 triggering...
This circuit appeared in a noverber 1962s Practical Electronics. The magazine is no more, but the...