Advertisement
Well protected
→
Today, electronic alarm systems protect
many valuable objects, such as cars, and
buildings, such as banks and apartments. A
loud siren or a wildly flashing alarm light will
usually drive off an intruder pretty quickly,
because it attracts a lot of attention.
Intruders can often even be frightened just by
seeing that an alarm system has been installed.
Holdup alarm systems serve to respond to
break-ins or notify a security service or the
police in case of a stickup.
How do real alarm systems work?
→
They operate in pretty much the same
way as the system you built: during a break-
in, a burglar will trip a hidden switch, which
will break a circuit, thereby triggering the
alarm. The circuit in an alarm system is
called a "zone." Such switches are located
around windows and doors. If a burglar
opens the window or door, it will sound a
siren or an alarm light will go on.
Alarm Systems
CHECK IT OUT
Access control
There are also other methods,
though, to deny access to
unwanted persons. This kind of
system only lets people into a
building if
they know
the right key
combination.
27
Advertisement
