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DIY – Alarm System Monitoring – Step 2

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This entry is part 2 of 5 in the series Designing Your Alarm System

Central Station Monitoring – Should you do it?

Your alarm system can be a local type of alarm or it can be connected so that it will communicate with a Central Station where the authorities can be notified. The alarm system will send in a different type of signal for each type of alarm event. The typical events are Intrusion Alarm, Fire Alarm and Emergency Alarm. Depending on the type of alarm the appropriate authorities will be dispatched. This is obviously of great value since you would not want the paramedics to come for a security breach. On the other hand if your alarm is a local type of alarm the security system will not do anything except sound in your home and ring a bell if one is connected. This does you no good if you are not home when the alarm is triggered other than to scare the burglar off. There is another type of communication that seems to be gathering popularity and that is self monitoring without dispatch from the central station. With the newer types of alarm systems using cellular communication the alarm can be accessed from any internet connection with the user receiving the alarm. This is called self-monitoring and is less expensive than having a central station but many alarm companies do not offer this in any alarm monitoring packages.

Types of Alarm Monitoring

The end result of alarm system monitoring is that when the alarm is triggered the central station will receive the alarm and be able to dispatch the appropriate authorities. How the signal reaches the central station varies drastically. The following are the different types of monitoring:

  • POTS Monitoring
  • VOIP Monitoring
  • Cellular Monitoring


POTS (Plain Old Telephone Service) Monitoring

This type of alarm system monitoring has been the standard for years. It has always been very reliable but has always been vulnerable. It literally takes only minutes for a burglar to find the phone line coming into your home and cut the line. Once the line has been cut the alarm system “wants” to notify the central station but has no ability to transmit the signal.

While it provides limited features, low bandwidth and no mobile capabilities, POTS reliability is an often cited benchmark in marketing and systems-engineering comparisons, called the “five nines” reliability standard. It is equivalent to having a dial-tone available for all but about five minutes each year.

VOIP Monitoring

How VoIP Alarm Monitoring Works

Regardless of which type of provider is chosen, the fundamental principle is that the analog voice or analog alarm signal from a control panel must first be converted into a digital format using a chosen compression method. Then the signal is translated to a series of Internet packets that are routed over a network (either a managed network or the public Internet). This process is then reversed at the other end so that the person hears the voice or an alarm receiver can hear the alarm signal that was sent.

Problems with VoIP

Those VoIP providers that use the Internet, not a controlled network, are subject to the possible delays of the Internet. For instance, when the Internet is slow, this can cause digital communications to slow down as well. If you send a digital signal over this network during such times, the timing is thrown off. The arrival time of the individual packets could be slowed.

For example:

Honeywell ADEMCO Contact ID sends 1 signal in about 1.4 seconds. If the Internet is slow it could take 4-5 seconds for a signal to be transmitted and re-assembled, thus causing communication failures.

Another limitation of VoIP in general is when you lose power; your phone service is also down.  There is no power provided by the VoIP provider like a traditional phone company. Furthermore, when a failure of the VoIP network occurs, some equipment leaves the voltage on the phone line, thus the panel believes there is no problem with the circuit when in fact there really is. There are other limitations when trying to upload/download. The alarm panel may not answer or may connect, but will not allow you to upload or download the program.

Cellular Monitoring

GSM security system monitoring allows you to utilize the cell phone towers to transmit your alarm signals. The same information that was previously sent over a POTS line is sent via cell. There is no cell phone per say involved. The alarm panel has the ability to transmit the date directly to the central station with all of the same date that is required to dispatch the authorities. This form of monitoring provides the best features and the most reliable form of communication.


See Step 3 of Designing your Home Security System – Home Automation

Designing Your Home Security System
Monitor or not to Monitor
Home Automation
Choosing your Brand of Home Security
DIY or Professional Installation


Series NavigationDIY-Home Automation – Step 3 >>
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