The present invention provides a central terminal (10), and method of operation of such a central terminal (10), for managing calls between a telephone exchange (500) connectable to the central terminal (10) and a plurality of subscriber terminals (520), the central terminal being arranged to communicate with the subscriber terminals (520) via wireless links (515). According to the invention, the central terminal (10) comprises a call manager (560) for receiving a call from the telephone exchange (500) or from subscriber terminals (520), and for generating a call instance to represent said call, the call instance having a plurality of attribute fields to store attributes defining the call, at least one attribute being provided by the call. Further, the central terminal (10) comprises a storage unit arranged to store a matrix of interrelated data elements, accessible by the call instance, for enabling other attributes of the call to be determined from said at least one attribute provided by the call, the call instance being arranged to store these other attributes within the appropriate attribute fields of the call instance.