The unit is fitted with a SIM Card.
When access is required, a call is made to the phone number of the SIM Card within the GSM Gate Opener.
The unit allows to call to ring once, to acknowledge the call and to allow the unit to read the number calling it - Caller ID
If the unit is set to allow any caller, or to use Caller ID access, it looks for a match of phone numbers in its database and if found activates the on-board relay. If there is no match the call is simply ignored.
Have you ever had a call to your mobile and you don't want to talk to the person calling and press the RED button on your phone? These systems work in exactly the same way.
As the call is immediatly disconnected and a connection is never made, there is no charge for the call.
If a match is found a signal is sent to unlock or open the gates or door it is connected to.
If a match is not found, the caller is ignored.
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