This 80's General Electric circuit is guarded by the noise-guard for operating current. The circuit has an input sensitivity of 3 pA. The font must be symmetrical.
This circuit, with printed circuit board included, is from a Radio Electronics magazine from July...
In the figure we show how to excite a CMOS port by interrupting light on a Darlington...
We found this circuit in an old documentation, but it uses components that are still common in our...