Sensors And Actuators - Brother FAX-170 Service Manual

2.4

Sensors and Actuators

This equipment has two photosensors and four mechanical switches as described below.
Sensor name
Document front sensor
Document rear sensor
Paper empty (PE) sensor
Cover sensor
Hook switch sensor*
Cutter home position (HP) sensor
(*In those versions equipped with a Binatone handset, the hook switch sensor serves no function.)
• 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.
These photosensors are of a reflection type consisting of a light-emitting diode and a light-
sensitive transistor. Each of them has an actuator separately arranged (see the next page).
When an actuator is not activated, its white end lies in the path of light issued from the light-
emitting diode and reflects its light into the light-sensitive transistor. If a document is fed in
so as to activate the actuator, the actuator's white end goes out of the light path. With no
reflected light to go into the light-sensitive transistor, the sensor detects the presence of
documents.
• PE sensor which detects when the recording paper runs out.
• Cover sensor which detects whether the control panel is closed.
• Hook switch sensor which detects whether the handset is placed on the handset mount.
• Cutter HP sensor which detects the home position of the upper rotary blade of the auto-
matic cutter.
Each of these four sensors has an actuator separately arranged (see the next page). If an
actuator is activated, its lower end releases or pushes down the lever provided on the corre-
sponding sensor so that the sensor signals the detection.
Approx. 0.7 mm
Light-
emitting
diode
III – 15
Type
Photosensor (PH1)
Photosensor (PH2)
Mechanical switch (SW1)
Mechanical switch (SW2)
Mechanical switch (SW3)
Mechanical switch
Path of actuator's end
Glass
Light-
sensitive
transistor
Photosensor
Located on
Main PCB
Main PCB
Main PCB
Main PCB
Main PCB
Drive unit