Posing what could prove a serious challenge to Reuters Plc, AT&T Co and Telerate Inc have agreed a 50-50 joint venture to offer a foreign exchange transaction service based on Telerate’s existing foreign ex-change information service. Traders presently get information on their screens but the execute their trades by phone. The service will initially be designed to operate on MS-DOS micros and Telerate will design the system while AT&T will do the worldwide network. The service will be extended into metals, fut-ures and other areas later. There is no date for start of the service, which despite AT&T’s optimism may run foul of Judge Greene. AT&T killed a similar deal with Quotron Inc when Citibank bought Quotron.