The transistors used (a 2N3055 npn and 2N2955 pnp in TO-220 packages) are reasonably good choices. They should be placed on a heat sink for good heat dissipation.

An NPN sensor is a ‘sinking’ sensor because it sinks the output to ground whereas a PNP sensor is a ‘sourcing’ sensor because it provides positive voltage to the output. Below you can see the standard ...

When combined, these four modes define the operating qualities of dc photoelectric sensors: n.o. npn, n.o. pnp, n.c. npn, and n.c. pnp. The four-in-one sensor combines all four output types into ...