This circuit was found in documentation from the 1970s. However, it can be implemented with modern transistors such as 2N2222 for Q1 and BF494 for Q2. The crystal depends on the desired frequency.
This simple alarm with integrated CMOS sounds a piezoelectric transducer when the sensor circuit...
This circuit can be used to add a delay to a logic signal as shown by the input and output...
Suitable for recovering tape recorded media from a common tape player mechanism, this circuit is...