British Telecommunications Plc has launched an international asynchronous transfer mode service, having completed a pilot service which began in December 1996,(CI No 2,958). The service links BT’s national CellStream service to its partner MCI Communications Corp’s US HyperStream service. BT is aiming the service at corporations who wish to connect to an international network, as an alternative to more expensive leased line connections. CellStream offers connections in 1Kbit increments, contrasting, says BT, with leased lines that are restricted to 2,8,34 or 140Mbit lines, and uses Permanent Virtual Circuits whose bandwidth can be altered by BT in eight hours. CellStream also offers the ATM features of guaranteed quality of service, and voice, video and data transfer over the same connection. The international service has been trailed by NetCom Internet Ltd, with a 3Mbps segment of the 45Mbps link on the TAT-12 and TAT-13 SONET transatlantic cables. BT will expand its available bandwidth as the service expands. In the ATM services market, BT competes internationally with Cable and Wireless Communications Plc, and nationally with, Energis Ltd and the Integrated Communications Network, a consortium of cable providers. BT is sensitive about CellStream costs, but it appears that leased lines are approximately double the price of comparative ATM circuits. BT also has a Switched Multi-Megabit data service running alongside CellStream, but is only suitable for data services. The company plans to expand CellStream to Europe and is testing a pilot UK-Norway service with Norwegian telco Telenor A/S, already a BT partner in the Viag Interkom GmbH German mobile phone venture, along with Munich-based German conglomerate Viag, (CI No 3,095).