Brother FAX-921, MFC-970MC, FAX-931 service manual Sensors and Actuators

2.4Sensors and Actuators

This equipment has five photosensors and two mechanical switches as described below.

Sensor name	Type	Located on
Document front sensor	Photosensor	Control panel PCB ASSY
Document rear sensor	Photosensor (PI2)	Main PCB
Paper-edge sensor	Photosensor (PH1)	Sensor PCB
Paper ejection sensor	Photosensor (PH2)	Sensor PCB
Ribbon sensor	Photosensor (PI1)	Main PCB
Cover sensor	Mechanical switch (SW1)	Main PCB
Hook switch sensor*	Mechanical switch (SW1)	Hook switch PCB

•Document front sensor which detects the presence of documents.

•Document rear sensor which detects the leading and trailing edges of pages to tell the control circuitry when the leading edge of a new page has reached the starting position and when the scan for that page is over.

•Paper-edge sensor which detects the leading and trailing edges of paper and the presence of paper as well as detecting whether the paper front cover is closed.

•Paper ejection sensor which detects whether a paper jam has occurred.

•Ribbon sensor which detects whether the ink ribbon is loaded.

These photosensors are a photointerrupter consisting of a light-emitting diode and a light-sensitive transistor. Each of them has an actuator separately arranged (see the following pages) except that the paper-edge sensor has two actuators for sensing the paper and the paper front cover. When an actuator is not activated, its black end lies in the path of light issued from the light-emitting diode and interrupts its light so that the emitted light does not enter the light-sensitive transistor. If a document, paper, or ribbon comes in so as to activate the actuator, the actuator's black end goes out of the light path and the emitted light enters the light-sensitive transistor. This way, the sensor detects the presence of documents, paper, or ink ribbon.

•Cover sensor which detects whether the recording paper cover ASSY is closed.

•Hook switch sensor* which detects whether the handset is placed on the handset mount.

The cover sensor has an actuator ASSY (consisting of two actuators and a spring). If you open the recording paper cover ASSY, the actuator ASSY pops up to release the sensor.

*Not provided on the FAX-910.

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