ions Asynchronous operation uses the clock internal to the modem. and underpinned by cost savings achieved in switching from 4 wire Synchronous operation, which requires timing information to be leased circuits to 2 wire dial up circuits, the upper modem limit of passed with the data, uses a combination of internal, system and 30kbit/s imposed by the copper loop is however rapidly being external clock sources. A synchronous link requires a master clock reached. Compensating for this are a number of new emerging source, either generated internally by the modem or externally by markets. At the low speed V.22bis commodity end where ISDN, for data terminal equipment at one end. At the remote end the modem the time being at least, is less of a threat, a new market place has uses the system clock option to synchronise its received and trans- developed for the portable, laptop and now palm top computer. mitted data to the master. Miniaturised battery powered and increasingly integrated modems are being used to connect the business traveller from the home, hotel or even the car to the office for data transfer. These will inevitably 39.5.2.14 Management be looking to upgrade to V.32 technology and beyond. In the high speed modem sector, the 15 million Group 111 anal- Essential for the corporate network running business critical appli- ogue fax terminals installed world-wide represent a major oppor- cations, modem management is sold as either a software package or tunity (Braue, 1991). Currently using V.29 and V.27 technology they a complete hardware and software solution. Typically locally at- are expected to upgrade to V.32 and V.32bis within one year. Some tached to a centrally sited racking system and driven by a personal vendors have already grasped the facsimile opportunity by building References 39/13 these facilities onto battery powered, pocket size, V.22bis modems of the application, the expected traffic, connection and equipment with a view to keeping the mobile business man in constant touch. charges must all b