Introduction To Burglar Alarm Systems

Ari Erenthal
Published Jan 04, 2017 17:32 PM
PUBLIC - This article does not require an IPVM subscription. Feel free to share.

While alarm systems are popular, balancing between the right level of protection, the appropriate components and an acceptable price can be very challenging. This in-depth tutorial explains each fundamental element, offering guidance on the pros and cons of the most common options available. We review: 

  • Cost
  • Alarm Devices
  • Keypads and keyswitches
  • Inputs
  • Contacts, Motion Detectors and Glass Break Detectors
  • Wireless
  • Dialers, Sounders and Strobes
  • Panels
  • Central Station vs DIY
  • Communications With Monitoring
  • Licenses and Fines
  • UL Listing


Basic intrusion detection equipment is extremely cost efficient, with products available for any budget and threat level. Traditional alarm panels range from less than $50 to more than $500 online. Basic sensors are inexpensive as well. Wired magnetic contacts sell for as little as $2, and wired motion detectors sell for ~$25. However, upfront installation costs and recurring fees for monitoring cause the total cost of ownership to quickly rise. Hub based DIY systems and self monitoring have helped bring these costs down, but these systems are often inadequate for all but the simplest intrusion detection scenarios.

Installation cost is highly variable, depending on factors such as the distance between the devices and the main panel, the number and construction of walls in the building, and the type, number, and age of the windows and doors in the building. Aesthetic concerns can quickly run up the cost as well. The difficulty and importance of concealing wires and sensors add to the time and technical knowledge required on the part of the installing technician. Experienced technicians can snake wires and install hidden sensors recessed into the frame of a door or window, but this takes time, adding to the labor costs. Wireless contacts and sensors exist, but they are more expensive than their wired counterparts, sometimes significantly so.

Monitoring is without a doubt the largest expense incurred by owners of intrusion detection systems. Most professional integrators, both independents and nationals, charge between $20 to $60 for monitoring, depending on quantity and quality of services offered. Integrators usually require end users to sign a monitoring contract, often 2-3 years or longer.

DIY / Self-Monitoring

At these rates, even discount alarm monitoring overtakes the cost of most equipment in a year. For this reason, Silicone Valley startups are beginning to offer self-monitored systems, sometimes to the annoyance of the alarm industry. DIY systems typically do not require yearly contracts, making them attractive to renters and others who do not want to get locked into contracts. Many DIY systems include self monitoring options, alerting users' smartphones when detecting a fault, or tripped sensor, such as an open door. Professional monitoring without contracts from companies such as Alarmgrid and are available for traditional panel based alarms.

Alarm Devices

When designing an intrusion system, you will be able to offer an enormous number of components to suit your user's needs. These components fall into one of three categories: 

  • Control
  • Inputs
  • Outputs


These devices are used to operate the system.

The most common device in this category is the keypad. Typically, it consists of a 12-button (0-9, *, #) numeric keypad, along with some function buttons. The user enters his or her code, and then pushes the appropriate function button, such as armed “away”, armed “stay”, disarmed, and so forth. The keypad will then show basic system status information to the user. Fixed displays will show this information in the form of either a light or a number representing a zone.

LCD keypads with alphanumeric screens can be programmed by the integrator to display more pertinent information, and are popular for larger jobs. Showing the user exactly which door, window, or motion detector is faulted is more useful than a light or a number, as the end user does not have to try and remember what zone the number corresponds to. However, programming these types of keypads will take an experienced technician several hours to do, leading to increased labor cost as well as increased equipment cost.

Graphic touchscreen keypads are becoming more common. Typically, these keypads are useful where the intrusion detection system has been integrated with one or more additional system, such as video surveillance, access control, or home automation. Integrated systems such as these are usually too complex to be controlled by a simple one line or two line alphanumeric display.

Another control device is the keyswitch. Less common today than in the past, keyswitches can still be found in older installations, especially in commercial and retail locations. Keyswitches consisted simply of a key cylinder on a metal plate, often with green and red LED’s. The user inserted a key which turned in one direction to arm the system, and the other to disarm. Keyswitches used to be popular for retail locations, as it allowed the owner or manager to designate a trusted employee as a “key holder”. A key holder is a senior retail employee who is responsible for opening or closing a store. If the alarm can be armed and disarmed with a key, the key holder does not need to be given the code to the alarm, making it easier to safely fire them. The obvious risk here is that any who finds or copies the key may gain access to the system.

Some alarm manufacturers are beginning to offer smartphone apps that allow users to arm, disarm, and bypass their systems. These apps are quite useful when offering home automation integration.


These devices are the bulk of the intrusion detection system, and what are used to trigger alarms. 

Door/window magnetic contacts

In older systems, mechanical plunger or roller switches were used, but these devices have become less common, since they wear out much faster than magnetic contacts. Today, the most common contact is the magnetic contact. Typically consisting of a reed switch connected to a wire which causes the circuit to open and close when a the magnet comes close or moves away. Magnetic contacts come in multiple form factors, surface mount and recessed. Special application contacts are made for overhead doors, gates, and roof hatches. 

High security contacts

Standard magnetic contacts can be defeated by using a magnet, assuming an intruder knows exactly where the magnet is and can reach it. Double bias switches are more difficult to defeat, and triple bias even more so. In most applications, door contacts contain only one set of physical contacts, reed switch or otherwise. In some higher-security environments, however, each device may contain multiple switches, each with a corresponding magnet, and of the opposite polarity. This makes these contacts more resistant to defeat by an external magnet, since applying the magnet wrong will actually put the door into alarm by forcing a contact of opposite polarity to close. Magnasphere uses a unique spherical magnet which they claim is more defeat resistant than even triple bias reed switches, and which is UL 634 compliant

Motion detectors

Motion detectors are the second most common device used. Most of these devices use passive infrared technology, but other options exist, such as microwave, ultrasonic, and active infrared. Large microwave detectors are typically used for perimeter detection in outdoor high-security environments. Ultrasonic and active infrared detectors are rarely today. Dual-technology detectors, which uses microwave and passive infrared together, require both technologies to detect movement before it will send a fault signal. Using dual technology sensors reduce the chance of false alarms. 'Pet immune' dual technology sensors can only be tripped by subjects that weigh more than 80 pounds, preventing cats or dogs from setting off the motion detector while still protecting the detection area from human intruders.

Glass break sensors

Two types of sensors are capable of detecting the sound of glass breaking. Contact detectors are attached directly to a pane of glass and sense frequencies of glass breaking. These work well for individual windows. To cover several windows or panes of glass at once, audible detectors are more efficient. These sensors listen for the sound of breaking glass and are typically wall or ceiling mounted about 20’-25’ away from the glass. Many audible glass detectors have adjustable sensitivity levels, and thorough testing is required before use. If the sensitivity is set too high, the sensor may cause false alarms. If set too low, the sensor may not go off at all. 

Hold-up switches/panic buttons

Panic buttons are used to request police response through the alarm monitoring company. Banks normally install hold up switches at every counter and train tellers to covertly activate them in case of robberies. Some banks choose to use money clip switch, which sends a silent alarm when a specific bill is removed and given to a robber. Other banks prefer a foot switch, which can be secretly activated with one's hands raised. Still others prefer a simple button, which can be installed under a counter.

Alarm screens

For residential customers who want to be able be able to keep their windows open while still keeping their alarms armed, integrators can have made custom window screens made. These screens have thin wires woven through the mesh which will set the alarm off if cut. The frame of the screen has a magnetic contact which will set off the alarm if pushed in. 

Smoke and carbon monoxide detectors

Smoke detectors can be connected to intrusion detection systems. This allows homeowners to use the alerting and monitoring capabilities of the alarm system to alert people in the home to a fire or carbon monoxide leak, and to call the fire department. While commercial buildings require elaborate fire alarm systems which must be inspected and approved, single family residences often do not.


Vaults and safes are often protected with multiple alarm devices. Normally, in new installations, these are built into the safe when it’s built, but they may also be retrofitted. Vault sensors are designed to detect drilling, mechanical cutting, acetylene torches, thermal cutting, water-cooled diamond drills, water jet cutting tools, hydraulic jacks or explosives. 

Pool alarms

Several states require an alarm on swimming pools without automatic covers. In addition to alarms on gates, doors, and covers, which resemble standard magnetic contacts, some pool alarms can be triggered by anything disturbing the surface of the water. Some pool alarms are designed to float on the surface of the water, but these can register false alarms in high winds. Sensors that are installed below the surface of the water, mounted to the inside wall of the pool, are far more reliable. 


Intrusion detection systems can be used to alert users to environmental issues. Water sensors can be installed in basements and around boilers to alert in case of floods. Temperature sensors can warn users if the heat or air conditioning in an area has failed. Using these sensors in server rooms or vacation homes can let offsite users know of a problem, allowing them to send plumbers or HVAV technicians to fix it. 


In residential and commercial applications, wireless devices may provide substantial labor savings. Running cable through existing spaces is the largest labor expense in installing an intrusion detection system. While they may have great benefits, end users should beware of the drawbacks: 

  • Range issues: We have never seen a wireless security system that did not have range far below the manufacturer’s claimed range. In most cases, system specs will be quoted as open air range, with little indication of what can really be expected. We’ve found that metal stud walls render wireless devices nearly useless. In wood stud walls, we have seen devices work reliably out to about 200’. We strongly recommend users request that installing companies test wireless devices before installing them, to avoid potential problems.
  • Compatibility: Not every manufacturer of intrusion detection system provides compatible wireless devices. Universal options, such as Inovonics may be used in these cases, but require numerous input modules, and are far less streamlined than proprietary, integrated wireless solutions. Several manufacturers are now offering alarms with Z-Wave technology, allowing them to be used with third party access control and home automation products.
  • Battery Maintenance: While the rated life of batteries in wireless sensors is normally 3-4 years, users must keep in mind that this means they will be making a time and material investment periodically, to change all these batteries. Wireless sensors often use lithium-ion batteries, as well, instead of less expensive alkaline batteries.

Other Outputs

Once an input has been triggered, the system needs some way to notify the user of the fault. Often, integrators install the loudest horns and brightest strobes they can in order to scare off intruders as soon as possible. Others favor sending a silent signal to a central station monitoring company so that they can dispatch police or security. We believe that the first strategy is generally more useful, as unverified burglar alarms are generally low on the list of police priorities. One exception is panic buttons and hold up switches, which should be programmed to send a signal to the central station without sounding an alarm, allowing users to covertly call for help. After receiving a signal, an employee of the central station will usually try to call the end user, giving them a chance to stop the central station from dispatching police in case of a false alarm.  

This category basically consists of three types of devices: dialers, sounders, and strobes. 


Simply put, the dialer dials. Historically, this device was connected to a phone line, and upon alarm, it dialed one or more parties to notify them of the alarm. This could be a voice message or a data transmission. With the prevalence of the internet and decline in phone line customers, however, IP “dialers” have become much more common. Instead of actually dialing a central station, the IP communicator transfers this data via the Internet, where it’s received by a specialized receiver. The final option is the digital input monitoring interface. This device (such as the HW Damocles) sends an email when a device attached to one of its inputs is triggered. Most DIY alarms have this feature as a standard. 


This devices come in the form of piezo speakers, horns, or mechanical bells. Piezos are most common at this point. Horns are used when higher volume is needed. Bells have become much less common in recent years, but are still occasionally used. Keypads generally contain a piezo sounder that will beep upon alarm unless programmed to be silent.


Strobes are generally located on the exterior of a building to alert neighbors to alarm, especially when ordinances disallow audible alarms to be triggered. Many integrators install both strobes and sounders, and some manufacturers sell combination sounder-strobes.


When selecting an appropriate control panel, there are a few factors that need to be taken into account:

Capacity: How many devices will be connected to your system? This is the number one factor that must be considered when installing an intrusion detection system. Nothing else matters if the system is not large enough to support the number of devices. This may range from two to 500 devices, with options in between. Larger panels are normally of the addressable variety, which we’ll touch upon in a moment.

Partitioning: In an intrusion detection system, partitions refer to spaces within the building which may be armed and disarmed independently. This division may be because of different work units in a facility, such as admin and warehouse, or it may be multiple tenants within a building. Partitioning prevents installation of multiple panels, especially in the multi-tenant facility case, and should be considered when selecting a panel.

Addressability: To facilitate installation of larger systems, some panels support addressable devices. This allows a single circulating cable loop to be installed throughout a building, supplying power to all devices. The devices are then addressed (via DIP switches or other means), so they report to the panel as individual zones, instead of as a group. This saves substantial labor in large systems, since it avoids homerunning cables from distant devices to the panel. For everyday use, such as residential and small commercial systems, though, it is much less of a factor. In these smaller systems, running cables directly to devices is much less of an issue.

Wireless: Wireless capability varies between manufacturers as well as within each manufacturer’s line. Not every panel will support wireless devices, so this must be taken into consideration. Add-on wireless receivers may also be used, but these generally cost more than built-in wireless capability. We’ll discuss wireless more below

Functionality: For many integrators, the ability to remarket home automation to existing customers and the ability to sell automation devices as add-ons to alarm customers significantly contribute to their profitability. For this reason, choosing a panel that is compatible with OEM and third party automation products can be quite important.

Central Station vs DIY Monitoring

There are two fundamental ways for monitoring alarm systems - using central systems or self-monitoring.

Central station monitoring: The most common monitoring method for intrusion detection systems is via central station monitoring. The alarm panel is connected to the central station via telephone lines or IP. Signals are received and trigger events on operator's PC via automation software connected to the central station receiver. The operator follows procedures as outlined by the customer in responding to these alarms. This may be a list of staff to be called for certain alarms, such as environmental or trouble signals, while intrusions normally call for law enforcement to be notified.

Self-monitoring: While the vast majority of intrusion detection systems are monitored by a central station, some users choose to monitor the system themselves. This has been possible ever since the invention of automatic voice dialers, but is growing in popularity today due to the increase in the number of smartphones in use. This makes monitoring via email or web browser more easily possible. There are two main ways of self-monitoring a security system, neither of why are typically built into the panel.

Communications With Monitoring

IP communicators, an advancement in communicators in the past few years, provide a few advantages over telco dialers. Generally, they are more supervised. Where phone lines are checked once or twice per day by the central station, or sometimes not at all, IP communicators may be supervised at much smaller intervals (seconds or minutes), since the connection is always on. IP communicators also eliminate the need to install a landline for the security system, which may save $10-20 dollars per month if one does not exist.

Voice dialer: Voice dialers connect to relay outputs on the panel, which trigger one or more voice messages when the relay is activated. Basic dialers allow only one message to be recorded and triggered, while other models allow for two or more. Multiple messages allow voice notification of more than simply “alarm”. For instance, one message may notify the user of security alarm conditions, another, fire alarm, and a third, environmental troubles. The main drawback of this is that it requires a phone line. If cut, there is no supervision and no way of knowing that an alarm notification won’t be sent. Voice dialers can be found online for less than $100 dollars. obsolete?

Internet: To facilitate monitoring via web browser, email, or text message, Ethernet I/O modules are often used. These modules are connected to the alarm system in the same way as voice dialers. However, instead of dialing a pre-determined phone number, the module will send an email or text message to one or more addresses. Most also have an HTML or Flash-based web interface, to enable monitoring from a web browser. These modules are a bit more expensive than voice dialers, costing about $200 and up, depending on number of inputs.

Fire Response

Often called “Knox Boxes”, as Knox is the most common manufacturer, these lock boxes are mounted outside a facility and contain keys or access cards so that firefighters and other emergency staff may enter in case of emergency. The box is unlocked using a special key only issued to emergency services. Since this box is mounted on the exterior of a building, it is vulnerable to attack by criminals. Without some sort of monitoring, the box may be opened or removed without any notification. For this reason, lock boxes are commonly supplied with tamper contacts, which are connected to an input on the intrusion detection system. If the box is opened or removed, a tamper alarm is generated.

Licensing and Fines

False alarms are a major problem for intrusion detection systems. The two main control methods are licensing and fines.


Because false alarms can consume significant policing resources, some municipalities require obtaining a license per address / home / business. Typically, the license fee is under $100 and this approach is increasing in popularity across the US as alarm industry associations support this to reduce false alarms. Typically, if the license is required, the seller will help the user obtain the license. In some cases, the municipality will look to verify that the alarm / provider is of sufficient quality. Users should check what their local jurisdiction requires.


Some municipalities use fines to penalize false alarms. This varies by municipality. Approaches include:

  • An initial warning for first false alarm.
  • A fee charged per false alarm often in the $50 - $250 range.
  • After a false alarm, a requirement for the alarm provider to proof that any error or malfunction has been fixed.

Related, some municipalities will charge fines for alarm sirens that run / go off for too long, which has prompted some manufacturers to add an automatic siren cut-off after some time (with 4 minutes being a common default).

Like licensing, users should check how their local jurisdiction handles fines.

UL Listing

Insurance companies require certain high risk customers, such as jewelry stores, to install and maintain an intrusion alarm system that meets certain specific standards before they will issue a policy. These standards cover then type of equipment used, the methods used to install the alarm, the service schedule used to ensure regular maintenance and testing, and the central station used to monitor alarm signals. Becoming UL certified gives alarm providers access to more profitable customers, but requires using only UL listed equipment and installing that equipment in a more labor intensive way.

These listings are not typically required for home / residential systems.

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