Printronix L5000 Series Maintenance Manual page 264

Interface circuits
The developing unit has 2 sensors (toner density sensor and toner empty sensor), and
the toner supply clutch. AC and DC bias voltages are applied to the developing roller.
Toner density sensor circuit
The detection concentration of this sensor is set at 11% in the following circuit:
6–26
R86
5.1K
R217
10K
1/4W
VR11
CT–6P
10K
Electrical and Wire Data