trex features such as ring again and three-way calling. User response from US and Canadian field trials has been extremely Convergence of voice and data in digital networks is an accom- positive, particularly in the areas of audio quality, functionality of plished fact. A recent US survey of Fortune 1500 companies showed the display and ease of use. that despite the continued dominance of voice traffic in terms of Most of the functionality of these sets resides in the DMS-100 volume, data is the dynamic service requirement and driving force software. The sets themselves transmit messages corresponding to behind new applications. Local Area Networks (LANs) solved key depressions to the switch, and receive indicator messages from immediate data handling requirements at working group level. the switch. Because the terminals are unaware of the feature actually Local integration of voice and data at site level through a PBX invoked, new features can be added and old ones upgraded without delivered greater interconnection options. The use of private leased changing the installed base of terminal hardware or firmware. lines to interconnect sites created wide area data networks. The introduction of liquid crystal displays (LCDs) on some of the Digital Centrex brings the flexibility, capacity and resilience of business sets further improves the user interface by enabling, where the public network to wide area data networks as well as Integrated available, the caller's number and name to be displayed. There are Service Digital Network (ISDN) capabilities. also other reasons for the display, such as allowing the user to see Major offerings available from data services implemented on why a call has been forwarded, and from whom. Northern Telecom DMS digital public switches are: It is frequently postulated that most people in a business environ- ment only use about four features on their telephone system, mainly 1. Datapath services provide completely digital synchronous and because access to these features is inconvenient. T