There is an external white noise generator, which is used as a basis for (TRNG) True Random Numbers Generator. Two amplifier stages (LM358) aplify the thermal noise signal from inversely polarized base-emiter BC547. Amplification factor (determined by resistors 100K/5K6) should be adjusted so that there is no voltage clipping at AN0 input.

DC-DC convertor generates +9V2 and -4V2 for analog stage. Coils 2.2µH may be replaced by 0Ώ to 100Ώ resistors..