We found this circuit in December 1986, Radio Electronics magazine. It uses 3 inverters and has the frequency determined by the crystal. The power supply is 5 V.
The amplifier shown can either excite a speaker in this low power version, or its input step can...
This simple alarm with integrated CMOS sounds a piezoelectric transducer when the sensor circuit...
This is a commercial radio circuit from the 1960s. The circuit was found in a Japanese publication from...