We found this circuit in a 1965 magazine. The circuit can be assembled with current equivalent transistors and the precision in generating the frequencies depends on the tolerance of the capacitors.
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...