This has been described by some as a Solar Powered Intercom; However it is more than that. It works off the 3G GSM networks (and 4G with Optus only) and has no range limit as a consequence. You will need mobile phone reception at your gateway. So long as you have that, when a visitor presses the intercom’s button, this unit’s in-built ‘mobile’ phone dials the home owner’s phone. When the home owner answers, they can speak to their visitor and if they want to let them in, they need only press the # button on their phone to open the gate. This kit comes with the GSM intercom, the solar panel and 10 Amp batteries in a waterproof enclosure.
The GSM18V81S has a simple button for visitor’s to press. Within its shell is circuitry that can store 3 contact numbers (so that if the first resident misses the call from the gate, a back-up number rings so that another person can talk to the visitor at the intercom). There are other good features you can read about here (click).