GSM (Global System for Mobile Communications) & Electrical Installations
GSM is a telemetry system using cellular communications technology. A SIM card from one of the cell phone service providers is required to be installed in the GSM unit to enable communications between the unit and one or more cell phones and other GSM units if required. Most GSM units are suitable for mounting directly into a DIN distribution board. GSM units normally have easy step by step programming procedures to allow the end user to monitor and control various events. This programming can be done via a computer using the software supplied with the unit or via SMS using a security code. From a cell phone, it is possible to switch lights and other electrical circuits on and oﬀ, control electric gates, arm and disarm intruder alarm systems, control irrigation systems, etc. Intruder alarm systems can also be monitored via the GSM unit sending an SMS message to a cell phone or a number of cell phones of the end user’s choice giving details of which circuit has been triggered in plain text i.e. “lounge PIR activated”, “front door opened”, etc.
It is also possible to send an SMS message when there is a power cut or loss of power at the premises. This is very useful as it allows the end user, if away from the premises for a prolonged period, to make arrangements for the power to be restored before foodstuﬀ stored in freezers and refrigerators have time to deteriorate. The unit can also be programmed to send selective messages to individual cell phones.
Many GSM units have an onboard processor to enable functions to be performed on a regular basis by day and time, much like a time switch. This processor can also be programmed for logic functions e.g. If ABC happens then do something (turn on D for example). The advantage of this type of system is that the end user can monitor their premises no matter where they are providing they have cell phone coverage.