The frequency of this circuit depends on C1 and, for the indicated values, it is 1 kHz. Equivalent operational amplifiers can be used, and the power supply must be symmetrical.
This circuit was obtained in a 1979 publication. The operational amplifier is of the type with...
This circuit was obtained in a 90’s Popular Electronics. The frequency depends on C1, a component...
Because it uses TTL integrated circuits, this siren must be powered by 5 V or as indicated with D1 to...