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 circuit is a kind of Hertz Loop that can be used to check the operation of transmitters and...
This high-impedance headphone circuit was found in a 1990s William Sheets. The power is low, but...
Based on the 555, this circuit was obtained from Internet documentation, serving to generate a...