Optimus solo plus 4G 1 button GSM, surface mounted, with keypad. Dial to open, SMS alerts, 400 access codes, internal time clock, 2 relays, additional relays optional, exit release input, day/night feature, 2 year warrantyThe GSM intercom works with a SIM card and calls your landline number via mobile phone technology.To a visitor it appears to be like any normal intercom, they press a button, you pick up and you have a conversation. To open the gate you just press a number on your telephone. The intercom can be programmed to call and divert to several numbers, typically we set them up to call the landline first and divert to a mobile if not answered. If you don't hang up it cuts out after a certain time that we can adjust. Some of the advantages of this system are that you don't need to run cables back to the house/s, which can be pricey. You know if you have visitors even if you're not at home. You can still let them in for deliveries etc if you wish. You can also give the appearance of being at home even if you're away. This is good for security.The SIM can be set up on an "Intercom Lite" subscription€79.95 per year annual subscription which automatically renews and allow you to manage your subscription online2G, 3G and 4G compatibleSee Terms of Service @ https://gatesim.ie/#pricingOr you can supply your own SIM from the above supplier.There are other network available too, from different suppliers including Optimus themselves.The intercom can be programmed via text message which makes it cheap to maintain or adjust. There is also a 'dial to open' feature whereby if you call the intercom with your phone it will lookup the number of the person calling and if they are on the allowed list it will reject the call and trigger the gate to open. This effectively means you and a selected group can use your phones instead of radio fobs. This group can be edited via text message to the intercom. Other features and settings can also be edited via text message. If this sounds over complicated then simply use the intercom with its default simple settings which we will program for you at the time of installation. Nearly all new systems are using this intercom now and we always get very good feedback about them.