Upgrading Security - The Drinking Water - page 266

An arming station , which is the main user interface with the security sys-
tem, allows the user to arm (turn on) , disarm (turn off), and communicate
with the system. How a specific system is armed will depend on how it is
used. Although intrusion detection systems can be armed for continuous
operation (24 hours a day), they are usually armed and disarmed according
to the work schedule at a specific location so personnel going about their
daily activities do not set off the alarms. In contrast, fire protection systems
are typically armed 24 hours a day.
The control panel receives information from the sensors and sends it to an
appropriate location, such as to a central operations station or to a 24-hour
monitoring facility. When the alarm signal is received at the central moni-
toring location, personnel monitoring for alarms can respond (such as by
sending security teams to investigate or by dispatching the fire department).
The annunciator responds to the detection of an event by emitting a signal.
This signal may be visual, audible, or electronic, or a combination of these
three; for example, fire alarm signals will always be connected to audible
annunciators, whereas intrusion alarms may not be.
Alarms can be reported locally, remotely, or both locally and remotely. A
local alarm emits a signal at the location of the event (typically using a bell or
siren). A local-only alarm emits a signal at the location of the event but does
not transmit the alarm signal to any other location (i.e., it does not transmit
the alarm to a central monitoring location). Typically, the purpose of a local-
only alarm is to frighten away intruders and possibly to attract the attention
of someone who might notify the proper authorities. Because no signal is
sent to a central monitoring location, personnel can only respond to a local
alarm if they are in the area and can hear or see the alarm signal.
Fire alarm systems must have local alarms, including both audible and
visual signals. Most fire alarm signal and response requirements are codified
in the National Fire Alarm Code, National Fire Protection Association (NFPA)
72, which discusses the application, installation, performance, and mainte-
nance of protective signaling systems. In contrast to fire alarms, which require
a local signal when fire is detected, many intrusion detection systems do not
have a local alert device, because monitoring personnel do not wish to inform
potential intruders that they have been detected. Instead, these types of sys-
tems silently alert monitoring personnel that an intrusion has been detected,
thus allowing monitoring personnel to respond. In contrast to systems that
are set up to transmit local-only alarms when the sensors are triggered, sys-
tems can also be set up to transmit signals to a central location, such as to a
control room or guard post at the utility or to a police or fire station. Most fire
and smoke alarms are set up to signal both at the location of the event and at a
fire station or central monitoring station. Many insurance companies require
that facilities install certified systems that include alarm communication to a
central station; for example, systems certified by the Underwriters Laboratory
(UL) require that the alarm be reported to a central monitoring station.