The key components are the two transistors connected back to back. The first (Q1, pins 1, 2 and 6) is effectively used as a zener diode which will exhibit breakdown noise at low currents [1]. The second transistor (also labelled Q1 but on pins 3, 5 and 4) is used as an amplifier of said noise.<p>A similar circuit is explained in more technical detail here: <a href="http:&#x2F;&#x2F;www.nutsvolts.com&#x2F;magazine&#x2F;article&#x2F;bipolar_transistor_cookbook_part_5" rel="nofollow">http:&#x2F;&#x2F;www.nutsvolts.com&#x2F;magazine&#x2F;article&#x2F;bipolar_transistor...</a> (look for the &quot;WHITE NOISE GENERATORS&quot; chapter title)<p>[1]: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Noise_generator#Zener_diode" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Noise_generator#Zener_diode</a>