Jam Sensor (Pps - Printronix L5000 Series Maintenance Manual

Jam sensor (PPS)

This also is a photo–interrupter comprised of a light emitter and receptor and a lever.
It is located partway on the toothed belt. When the paper fold falls on this belt and
kicks the lever, the light passing between the light emitter and receptor is blocked,
and the sensor turns on. This sensor detects defective folding; if either the on–time or
off–time become longer than what is set, this is defective folding (error).
Optional Power Paper Stacker E–19