Ricoh BR-C1a Basic Service Training page 296

 Two methods of toner supply are used with this machine.
 Fixed supply
 PID control
 SP3400-001 determines which method is used
 "0" (Fixed Supply) or "1 (PID).
 With the "PID" setting, the machine makes a pattern on the
ITB at set intervals (see the next slide) and reads it with the
ID sensor.
 During toner supply control, it is very difficult to determine
the ideal toner/image density based only on pixel count
because errors tend to accumulate due to changes in
ambient temperature and humidity, deterioration of the
sensitivity of the drum over time, and variation in
development capacity. So, the "PID" setting (default) is
used.
Slide 296
 PID control is similar to the Aries.
Toner Supply Control
Overview
296
BR-C1 Training