Ricoh D392 Technical Training Manual page 36

Ring Type Detection
Sensor
Ring Cartridge Type Sensor (S805): Detects which type of
ring cartridge is installed (A4 or LT).
The A4 cartridge has a cover. The LT cartridge does not.
The sensor checks if the cartridge has a cover or not.
Slide 36
The photo on the right shows a cartridge without a cover [2]. This is detected as
LT.
36
D392 Ring Binder Training