We found this configuration in a 1990 Poptronics. The circuit can be powered by voltages between 6 and 15 V, changing the resistors in series with the LED. The frequency is set at R7.
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...