What are these transistors for?

[MBFX]

2N2712 Work-alike Noisemakers

These are General Electric made-in-Syracuse devices that we have sorted for creating noise in Zener mode. Test conditions + 15V through the device to a 1 Meg resistor to ground. Under test conditions, we guarantee 100 mv. p-p unamplified and no snap-crackle-pop. A typical basic circuit is here. The

synthcube.com

I have no idea how these are used, and I am curious.

 

[Bricksnbeatles]

the 2n2712 is one of many transisitors that makes an exemplary noise source when reverse biased. All kinds of white and pink noise generator circuits that use 2n2712s or other select BJTs, reverse biased, for noise sources