A method for improvement of contrast in an image shown on a display having a range of displayable video levels. Instead of obtaining the IP address from a location register of the IP PBX, the method involves use of a server configured to assign and provide to the caller’s communication device a unique address of a proxy. The method includes receiving user communications and control data transferred by a baseband unit. The invention makes it possible to mass-produce autonomous robots in units of interoperable functional modules. Movement limiting portions are retracted from a movable range of the lever to permit movement of the lever when the rear holder is in the fully locked state, but are in the movable range of the lever to limit movement of the lever when the rear holder is in the partially locked state. The XN-content in said extract is in the region of 10 mgkg-2 gkg xanthohumol.