Deciding whether to purchase a GSM alarm or GPRS communicating security system is a relatively easy choice once you understand the differences. Here we explain the signicant differences. GSM alarm security systems are the most basic. Customers are required to supply their own mobile phone SIM card, which can either be Pay as you go or monthly / yearly contract (although contract SIMs are the most reliable as they never run out of credit). GSM alarm are designed for users who only require activation alerts and status messages to be sent to between 1 - 10 mobile phones. These are ideal when system owners are based on or close to the site being protected and are happy that a simple text message is sufficient to alert them to an activation. Customers with higher security requirements or those needing a fully Alarm Receiving Centre monitored security system will require a GPRS security system. The GSM alarm wireless systems are programmed via a PC using a programming cable. Software is supplied on a CD or by downloading from our monitoring page. GPRS Security Systems. GPRS security alarm systems are more complex and flexible than GSM alarm security systems allowing them to be monitored via an Alarm Receiving Centre (ARC). These systems are supplied with a dedicated PRS SIM card.GPRS security systems are suitable for clients using multiple systems on multiple sites and/or those needing high levels of flexibility to cope with large numbers of people who require access to sites at different times.