Cross-platform application for smartphones, tablets and computers. The GTS UC-One communicator client is a solution for IP telephony, video telephony, presence and messaging – SIP client connected to the Internet with Instant messaging and Presence. It also has integration with GTS IP Centrex platform for various calling features. End-users keep a contact list in the client showing the presence status of their colleagues. From this single interface the end-users can easily initiate and receive phone calls, video calls and instant messages. The contact list is the perfect way to start multimedia communication, encouraging the users to smarter and more frequent communication.