Brother International FAX 275 Service Manual - Page 26

2.4

Sensors

and

Actuators

This

equipment

has

two

photosensors

and

four

mechanical

switches

as

described

below.

Sensor

name

Type

Located

on

Document

front

sensor

Document

rear

sensor

Photosensor

(PHI

)

Photosensor

(PH2)

Main

PCB

Main

PCB

Paper

empty

(PE)

sensor

Cover

sensor

Hook

switch

sensor

Mechanical

switch

(SW1)

Mechanical

switch

(SW2)

Mechanical

switch

(SW3)

Main

PCB

Main

PCB

Main

PCB

Cutter

home

position

(HP)

sensor

Mechanical

switch

Drive

unit

•

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

/

Path

of

actuator's

end

I.

\\

,---

Glass

i

Light-

Light

-

emitting

sensitive

diode

transistor

Photosensor

III

-

15

Brother International FAX 275 Service Manual - Page 26

Sensors, Actuators

Page 26 highlights