A GSM module containing a SIM card is included in or added to a security alarm panel by the Alarm Installer to allow reporting over the GSM Network, normally sharing with mobile phone services supplied by Telecommunications Carriers including Telstra, Optus, Vodafone etc.

Some systems also use the SMS (short message service) path to transmit signals but this should only be used for low priority messages not alarm conditions as SMS is a “Store and Forward” method with no time requirements for message delivery.

Where GSM is used it should be realised that on most occasions it shares the network with voice communications which contains many users, a voice priority in demand, a complicated switching between cells, and variance in signal strength.

CMS advises that Alarm Data over GSM Networks is sometimes corrupted and messages lost. It is not normally a polled system and as such is a backup to a dialler not a higher security option.

GSM over a VPN (virtual private network) is the highest availability and reliability and it is recommended that the user be aware of the limitations and should not compare the service to the Multipath IP or Emizon 21 Service or even the aging Securitel Monitoring. It is an alternative to Dialler Monitoring and as a Backup to Dialler Monitoring provides better availability.