License for VIP2SIP Gateway Art. 1456G, 10 licenses on a USB stick for receiving the door call on a SIP telephone system or a suitable third-party device, such as the GIRA G1. The door call is made on the SIP telephone system without a video image. The license is also used to use a reserved line so that a call back can be made to the door station and the calling door station, if there are several door stations, can be identified by name.