A Bell System bond issue -- long the bellwether of top-rated corporate debt offerings -- received a lukewarm reception from investors yesterday despite a record high yield of 11.47 percent.

Southwestern Bell Telephone Co., a unit of American Telephone & Telegraph Co., offered $450 million of 40-year debentures at a cost to the company of 11.58 percent. A Washington trader said some of the bonds remained for sale and that the offering was "no ball of fire."

The triple-A-rated debentures were brought to market by a Wall Street syndicate headed by Goldman, Sachs & Co., and about 75 percent of the issue was sold yesterday afternoon. Southwestern Bell's new issue is the first of a projected $4.5 billion to $5 billion in debt securities to be sold by AT&T and its subsidaries this year.

Separately, interest rates of up to 10.95 percent were announced for $2 billion of bond issues by the Federal Farm Credit Banks. For $755.5 million of 2-year, 9-month bonds the rate will be 10.95 percent; for $817.5 million of 5-year bonds the rate is 10.90 percent and for $438 million of 10-year bonds the rate is 10.95 percent. A national group of securities dealers and banks will offer the bonds.