We found this circuit in a 1957 Raytheon transistor publication. The circuit can be assembled with more modern transistors with minor changes. The handset must be high impedance magnetic.
This low noise preamplifier has a gain of 19 dB in the 30 MHz band. The circuit is from the 80s....
Found in American documentation from the 90s, this configuration detects the direction of rotation...
This circuit generates a 5.3 kHz linear ramp with the indicated components. The 7555 is the CMOS...