AGD has been specifying and installing Wireless GSM Intercoms with great success.
At the gate entrance you have a standard voice intercom front panel, this links to a module with a Sim card which rings through to your landline phone (via mobile phone network).
How it works
Visitor presses the intercom push button at entrance
Your house phone rings
You pick up and speak to the caller
To let them in simply press the designated button on your phone e.g. '#' button
No service trench/ducting – cost saving on ground works/cable runs
No internal routing of cables
Can use fixed landline phone operate gates or Cordless DECT phones which give even greater flexibility throughout the house
Can be set up to ring or divert to your mobile phone
You can ring into the system to operate gates remotely
Requires good mobile network reception area
More expensive initial layout – this is usually off set by cost savings against ground works and long cable run costs
Ongoing cost of calls (pay-as-you-go top up card or monthly contract)
AGD provides the sim card pack with initial call top up of £10
End user will need to periodically top up the card
NB: Call length can be restricted to 20-30 seconds to minimise call cost.