Elenco Electronics MO-1251 Manual do Utilizador descarregar pdf (Página 63)

0

2 SH INCHES

ALPHA MEDITATION

GOGGLES foil

pattern.

TS

3 0

o

ONO

2'3/46 INCHES

IR RECEIVER /RF TRANSMITTER foil pattern.

THEIR TRANSMITTER foil pattern.

2V5s

INCHES

RF RECEIVER

/ALERT

BEEPER foil pattern.

HOME

SECURITY

continued from page 37

built floor-the

nightingale

floor -

that creaked loudly when

walked

on.

A shrill sque

-e -e -k in the

middle of

the night was

certain to

bring on the

Sultan's personal

bodyguards.

The

modern nightingale

floor is

the

Teiresias,

Inc.'s

Pulsor Volumetric

Stress Detector,

shown

in Fig. 6. The

sensing

device

is an encapsulated

sil-

icon

bar that is

epoxy -cemented

to a

floor

beam. Any

deformation of

the

beam, no

matter how

slight, is

de-

tected by the

sensor, whose

process-

ing

amplifier

can tell the

difference

between the

stresses caused

by struc-

tural

shifts, the

patter of

the multi -

legged

feet

of household

pets (or ro-

dents),

or the strides

of

a

human.

When

the processor

senses

the

stresses

caused by humans,

it trips

a

conventional

alarm's protective

loop.

Wireless

protection

Wireless

detectors

and control

cen-

ters

are the latest

development

in

high -tech

home security.

As shown

in

Fig. 7,

a generic

representation

of

a

full -feature wireless

system

such

as

the

one offered

by Dicon

Systems,

Inc., the

control center

consists of a

radio receiver,

a super -sophisticated

computerized

control system,

and a

voice

synthesizer

that can give

user

instructions

and

voice

alarms. The

center

drives an internal

digital dialer

for a central station

and one

or more

other numbers

and announcements,

a

local

alarm bell

or siren,

and

it

can be

hard -wired

to a local

loop or

detector.

Its

real sensing power,

however,

lies in

individual

transmitters,

each having

its

own digital

code so that

the control

center

knows where

the alarm is

com-

ing from.

Although Fig.

9 shows

only

five

transmitters,

the center

can ac-

commodate

more. For

example, there

might

be two or

more transmitters

for

the

windows;

one for

upstairs, one for

downstairs,

and

possibly one for the

basement.

(It saves wiring

through

floors

and ceilings.)

Similarly,

there

might

be separate

transmitters

for the

front

and

back doors,

or multiple

transmitters

for fire

detectors and

medical

or panic

transmitters

(pen-

dant

transmitters worn

on

a

necklace).

Best

of all,

the system

can be con-

trolled

from

one or more

remote -con-

trol transmitters.

The

transmitters are battery

powered. They

are

supervised in that

their battery levels and

signal

strengths are checked regularly. If the

center determines that a battery

is get-

ting

weak,

it announces -by

voice,

beeper, or display -that the transmit-

ter's battery should be replaced soon.

The operating frequency for

wire-

less systems is usually in the 300 -

MHz band, so that the antenna can fit

in

the

small

transmitter cases.

Where

there are

reception problems,

the

equipment might

operate

on

40.8

MHz,

because the

lower

frequency

passes through brick and steel doors

and

walls with

less attenuation.

An important point to keep in mind

when

considering a home -security

system is that many installation ser-

vices

are familiar only

with

the equip-

ment

that they are authorized to sell,

or the stuff

they are used to using.

(Try asking a dealer if he knows of a

nightingale floor sensor.) If you think

you need a particular kind of protec-

tion, do not accept that it doesn't ex-

ist. In

this era of high -tech devices,

somewhere

out there someone

has

ex-

actly

what

you

want.

R -E

69

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