NY -- Standard&Poor's CreditWire 10/2/96 -- Standard&Poor's today has assigned its preliminary single-`A'-plus rating to SBC Communications Inc.'s (SBC) and SBC Communications Capital Corp.'s (Capital Corp.) unsecured debt securities, which may be issued up to an aggregate of $3 billion under a Rule 415 shelf registration. At the same time, Standard&Poor's has affirmed its single-`A'-plus corporate credit rating on SBC and Capital Corp., as well as its single-`A'- plus rating on Capital Corp.'s senior unsecured debt and its `A-1' commercial paper rating. SBC's consolidated debt outstanding is about $7.2 billion. In addition to the unsecured debt securities, the shelf registration also allows SBC to issue preferred and common stock within the aggregate total. Debt