Senate Majority Leader Robert C. Byrd warned yesterday that the American television manufacturing industry may be "extinguished" because of what he said were predatory Japanese pricing practices. He advocated low voluntary import quotas.

Byrd told reporters that he stated his fears Friday in a cable to the Chief U.S. trade negotiator, Robert Strauss, who is discussing voluntary quotas with Japanese representatives in London.

The West Virginia Senator said the Japanese, who accounted for an average of 8.16 per cent of U.S. television imports between 1971 and 1976, want a floor of no less than 2.5 million sets under their exports to the United States, while American manufacturers have suggested a 1.3 million limit.

"I'm concerned that even the lower figure we are talking about will not adequately protect our own industry," he said.

The U.S. International Trade Commission has found tht increased television imports are threatening serious injuiry to domestic manufacturers and has suggested higher duties.

"The Japanese manufacturers clearly seem to be working in concert with a unified plan that could ultimately lead to the destruction of our diminishing domestic TV industry," Byrd said.

These manufacturers have entered into an agreement with atheir government setting prices that undersell U.S. models by 10 per cent to 15 per cent, he noted. There are indications that the Japanese may be going further by paying rebates to American dealers who buy their sets, the senator added.

He drew a parallel with the domestic radio industry. American radio manufactures lost their entire domestic market between 1955 and 1973, he said, while the number of Japanese radios rose steadily and their average price rose from under $10 to $50.50 last year.