 But the national delegations showed little interest in compromise, each hoping that "their" system would come to define what was perceived to be going to be an enormous new mass-market.In 1980 CCITT therefore issued recommendation S.100 (later T.100), noting the points of similarity but the essential incompatibility of the systems, and declaring all four to be recognised options.Trying to kick-start the market, AT&T Corporation entered the fray, and in May 1981 announced its own Presentation Layer Protocol (PLP).