Telefonica de Espana SA has finally stopped sitting on the fence and has made up its mind to become an equal member of the Unisource NV, the telecommunications services joint venture of Telia AB, Koninklijke PTT Nederland NV and the Swiss PTT. Telefonica was already an associate partner of Unisource, but the letter of intent for it to become an equity partner was signed on Friday. It will participate in data, satellite, card, mobile, voice and carrier services within Unisource. The three initial partners in Unisource also plan to combine their international telephone networks, with an aim of grabbing an 18% to 20% of Europe’s worldwide telephone traffic by 2000. A subsidiary set up in Swtzerland, Unisource Carrier Services, will take the management and operations of the original parents’ international networks under one roof. Two weeks ago, Unisource became AT&T Corp’s WorldSource partner in Europe, taking a 20% cost-sharing stake in the company’s WorldPartners association.