4G GSM audiokits that are manufactured in the familiar modular 4000 series range with a 316 grade stainless steel matt finish. They are available from single call button applications up to 12 button kits (surface or flush), however is expandable up to 50 call buttons, all with the facility to divert to additional numbers if the first is busy or unanswered (up to 3 divert numbers per button). The 4G GSM intercom module is able to connect to 2G, 3G and 4G networks and is designed for global use