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Building a Better Alarm System with GSM Disclosure Number: IPCOM000007514D
Original Publication Date: 2002-Apr-02
Included in the Prior Art Database: 2002-Apr-02
Document File: 5 page(s) / 79K

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Aaron Twohig: AUTHOR


This paper explains how GSM technology can be used to create an alarm system that is more efficient, more reliable and more secure than current systems.

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 Building a Better Alarm System with GSM

 Aaron Twohig


This paper explains how GSM technology can be used to create an alarm system that is more efficient, more reliable and more secure than current systems.


Traditional alarm systems activate a loud siren when they are set off to alert people that a break-in is in progress. These are not suitable for remote properties, where it is unlikely that anybody will be within earshot. They also rely on the vigilance of neighbours or passing people to report the alarm to the relevant authorities. To overcome these limitations, newer systems use a phone line to alert the owner or authorities, via phone calls or signals to a central processing centre. However these systems also have problems.

Problems To Be Solved

It is expensive to maintain a constant PSTN connection between the alarm system and the monitoring centre. Because of this, existing systems either (a) make a call when the alarm is raised, or (b) make calls at regular intervals to report that the alarm has not been raised.

The problem with (a) is that the system is easily disabled by cutting the phone line. This has occurred frequently in this country (Ireland) in recent years, with petrol stations and small town supermarkets being targeted. The criminals are sophisticated enough to identify and disable the phone lines. The problem with (b) is choosing the interval length. A short interval leads to many phone calls, which is expensive. A longer interval will result in more time between a break-in and the alarm being raised, i.e. the criminals will have more time to get away.

Proposed Solution to the Problems

To overcome these problems, the alarm preferably uses a GSM connection rather than a PSTN phone line as a means of communication. The alarm has a simple GSM device that keeps switching from “active” to “stand-by” and back in the network. If the status of the device stops changing, then the alarm will be raised via an SMS message or a call to a subscriber or number or subscribers.

An existing alarm system can be modified to interface with a GSM device that repeatedly sends LocationUpdateRegister then Detach* messages to the GSM network. I will refer to this GSM device as a “Detach transmitter”. It could just be a cell phone that switches on and off. It must have an IMSI.

When the system detects a break-in it will stop sending the messages (see figure 1). This will mean that the Status associated with the IMSI in the VLR will stop changing from “Attached” to “Detached” and vice-versa.

A “trigger” or “active query” on the network’s VLR database will update a separate program whenever the status associated with that IMSI changes (see figure 2). This other program will be responsible for monitoring the “detach transmitter” and raising the alarm when necessary. This program will reset a timer associated with the GSM unit when the status of that GSM unit changes. If the timer expires, then the alarm will be raised via the SMS controlle...