Brother HL-5130 Service Manual page 94

CHAPTER 3 THEORY OF OPERATION
2.3 Sensors
2.3.1 Cover sensors
Detect opening and closing of the front cover.
2.3.2 Toner sensors
Detects if there is toner in the toner cartridge. The toner sensor at the left side emits light
through the window on the left side of the toner cartridge, then the toner sensor at the right
side receives it when the toner is low. They also detect whether or not the drum unit is
installed. (The toner cartridge is installed in the drum unit.)
Front cover sensor
Fig. 3-36
Toner sensor
(Light emission)
Fig. 3-37
3-24
Toner sensor
(Light reception)