| Security
zone - a zone is typically defined by a group of sensors
that monitor a specific area of the home or environmental condition.
For example, all the downstairs windows, the perimeter doors, or the
first floor interior spaces. Zones typically fall into three general
areas: the house exterior areas such as a driveway, pool area, or
entry area; perimeter entries or openings such as doors and windows,
and interior areas such as room, hallways, or stairwells. A zone can
also be assigned to safety related sensors such as smoke and heat
detectors.
Security systems can
generally monitor 8 to 16 zones. What the system does when an alarm
condition occurs in a zone is programmed into the system when it
is installed.
Armed/Unarmed - A security system is said to be armed if it will cause an alarm
condition if a sensor input detects a condition that may threaten
life or property. The alarm condition may turn on sirens, lights,
and/or transmit the condition to a monitoring service (see below).
A system may monitor sensors and report their condition for purposes
of home automation functions without being armed.
Sensor - a sensor is any device that detects a condition that can be translated
into an open or closed state. Sensors generally fall into three
categories; intrusion sensors (the largest category) intended to
detect actions associated with breaking into a home such as door
and window magnetic sensors, fire related sensors such as smoke
and heat sensor, environmental sensors such as water or carbon dioxide
sensors, and medical related sensors such as medical alert pendants.
Monitoring - A security system is said to be "monitored" if an alarm
condition (or other conditions programmed into the system) causes
the system to transmit its alarm state to a service that will take
appropriate action. Almost all security systems are capable of being
monitored by a security service. For a monthly fee the service will
call and dispatch local fire and police services as well as notify
the home owners. The monitoring service acts as a "go between"
the security system and local police/fire/medical services since
these services will not accept calls directly from the security
system.
Security System
Overview
Security systems fall into two general categories: stand alone systems
that operate independently from any other system in the home, and
integrated systems that are usually part of a home automation system.
Often the distinction between a home automation system and a security
system is blurred and it is hard to tell whether a system is an
alarm system with added home automation related functions, or a
home automation system with security functions built-in.
This guide will separate
the two systems and discuss stand alone systems followed by systems
integrated with home automation systems.
The other major division
of systems is based on how the sensors or other input/output devices
connect to the system: hardwired meaning they connect primarily
by cables; or wireless meaning they connect primarily by RF signals.
Wired and wireless systems operate almost identically and are primarily
intended for new construction installation and retrofit installation
respectively.
Typical security system components
The panel is intended to be mounted in the equipment
room or central distribution point in the home-the same location
that structured cabling or other equipment is located. It contains
the main control logic electronics of the system.
The
cables to all sensors and other devices (keypads, alarms, etc.)
originate at the panel. Most panels use an external 12 or 24 Volt
power supply, plugged into an outlet strip but some have a built-in
supply. They will always contain a backup power battery to supply
power to the system, typically for 6 to 12 hours, if house power
fails. The battery will furnish power for everything attached to
the system (for wired systems). The panel will also monitor battery
power and provide an alarm condition if the charge state is too
low. Programming the system is typically done by attaching a PC
to the system at the panel.
The keypads provide the user interface for the system.
They may be very simple, using only a few buttons and LEDs, or very
sophisticated with graphic displays and a range of alpha, numeric,
and special function keys. Most systems can accept several keypads
that act in parallel. Keypads are usually placed near entryways
to the home such as a front hall, back hall, and in the master bedroom
so the system can be easily armed or disarmed when leaving or returning
home. Keypads will always have a way to arm and disarm the system,
with keys to allow the user to input an access code (usually 4 to
7 numbers).
Sensors are remotely located throughout the home to detect some action that
causes the panel, depending on security state of the home (armed,
disarmed, and so on), to either do nothing, cause an alarm condition,
notify the occupants, notify a monitoring service, and so on. While
there are dozens of different types of sensors, from simple magnetic
door sensors to complex microwave motion sensor, they all produce
the same "output": either the sensor is "open",
meaning an electrical circuit path is open, or "closed",
meaning an electrical circuit path is made. For example, the contacts
on a magnetic door sensor is usually closed when the door is closed
and open when the door is open. The security panel simply detects
an electrical open or closed condition and is unaware of what type
of sensor is attached. Since all sensors work basically the same
way, they can be substituted or combined in almost any combination.
Alarm
devices provide some highly audible or visual indication
that an alarm condition has occurred. The most common are sirens,
bells, or horns that provide a loud alarm noise to alert occupants,
neighbors, or the police. Alarms come in both inside versions (to
alert occupants) and weather resistant outside versions. Outside
alarms can also be placed in protective enclosures. Alarm devices
are also available that output voice messages such as "Intruder
alert", "burglary, burglary, the police have been called",
"fire in upstairs bedroom", intended to scare away intruders
or give occupants more information about the alarm condition.
Annunciators
are similar to alarm devices but are used primarily to alert occupants
to anything from door openings, to someone around a pool area. They
can be simple buzzers, chimes, or voice generators.
A monitoring interface allows the alarm system to
use a security monitoring service. A monitoring service will notify
the police, owners, your company, or anyone else on a notification
list if an alarm occurs. They can also be used to filter false alarms
by calling the house to verify if an alarm was accidental. A monitoring
interface (usually built into the panel electronics) typically uses
a phone line to dial the monitoring service computer system. Once
connected, the interface will convert the alarm condition to a standardized
digital code that is transmitted to the monitoring service. The
monitoring interface can also use a cell phone connection or other
wireless system to connect to the monitoring service.
Sensor wiring for series and parallel combinations
Sensors that have normally open contacts can be wired together with
other normally open devices in parallel. If any sensor is closed
(alarm), an alarm will be detected. If more than one sensor enters
a closed state, it is not possible to tell which sensors are in
alarm.
Many
sensors, such as smoke detectors and infrared motion sensors, require
DC operating power, usually 12 volts DC. This power is usually provided
by the power supply in the panel and wired to the sensor using an
extra set of wires in the cable from the panel to the sensor.
Perimeter
zones are on the house perimeter and usually consist of
entry doors, garage doors, and windows. Perimeter zones are used
to generate intruder alarm conditions as well as for monitoring.
Interior
zones are on the inside of the house and typically include
motion sensors on each floor, halls, or basements, but can also
include sensors on cabinets, drawers, or other interior locations.
Interior zones are also used to generate intruder alarms as well
as monitor for activity.
All systems
include one or more fire/smoke "instant alarm" zones used
for attachment of smoke and/or fire sensors. There may also be a
"panic" or "medical" zone. A panic zone can
be connected to buttons or other sensors activated by the occupants
to indicate that an intruder has gotten into the house (perhaps
disguised as a salesman). This will cause a "silent" alarm
to be sent to the monitoring service to summons the police.
A medical zone
is usually assigned to buttons or wireless pendants around the home
that, when activated, will cause a medical alarm and alert the monitoring
service to send medical help.
The security
system will generally provide for a fixed maximum number of zones
that can be wired to the panel. Each zone consists of one or more
sensors wired together in either a series (most common) or parallel
configuration.
In some systems,
the function of each zone can be programmed, while in others, they
are fixed and defined by a specific set of screw terminals in the
panel where the sensors for the zone are attached.
Programming
Most security systems allow the installer to custom program the
system for the individual installation. Some of the more typical
programming parameters include:
pass-codes - one or more multi-digit codes for the occupants.
entry/exit
delay - the entry and exit delay times in seconds.
zone
operation - assignment of zones to exterior, interior,
perimeter areas or inclusion in each type of arming mode.
alarm
conditions - what to do when an alarm is detected (sound
alarm, annunciation, notify monitoring service).
monitoring
parameters - monitoring service information such as account
numbers, alarm codes, etc.
Programming
can be done from the keypad (upon entering a "supervisor"
or "installer" code) or by an attached PC via an RS242
port on the system panel. Once programmed, the system will retain
the input values in a nonvolatile memory to prevent loss in case
of power failure.
Wireless
Systems
While wireless security systems are primarily intended for installation
in existing homes, there is no reason they can't be installed in
any home. Wireless systems operate nearly identically to wired systems
except the connection to the sensors (or other components) is by
RF signals.
This means that
all the sensors will need to have a battery. Typically on small
sensors such as magnetic door and window sensors, the sensor is
actually hardwired for a short distance to the RF transmitter unit.
The transmitter can be mounted out of sight behind curtains, blinds,
and so on. Connection to alarm devices is also via RF. Alarm device
may plug into an AC outlet but may also be battery operated.
Typical security system panel with plug-in
power supply, backup battery, and keypad. The processor board has
screw
terminals to connect sensors alarms and keypads.
We
carry more than 10 different security systems please ask us which
one is the best for you |
