This circuit was obtained in an Electronics World of 1968. The operational amplifiers ones are types of the time, no longer used today. The circuit responds from less than 20 Hz.
Two tone siren (CB9085E) This circuit was found in a 1980’s Radio Electronics. The signal must be...
Found in an American publication from the 1980s, this circuit can be found in commercial sound...
We found this circuit in an 80's Radio Electronics. The circuit uses a PTC sensor and an LED...