[Karl] rerouted the trigger signal from the relay to his own 2N2222 transistor. This way the device can switch loads running at voltages other than its own 1.2V operating level.

For the full-stack job, they just give you a pile of 2N2222 transistors. (The first company wasn’t a great fit, and I eventually found a place that gave me some 2N2907s for the interview.) ...

Certain types of discrete transistors, the NPN 2N2222 and the PNP 2N2907, can be operated as inverted mode switches where “inverted” means that the collector is made to serve as an emitter and the ...