A union representing 102-thousand employees of S-B-C Communications Incorporated says it will stage a four-day strike against the company starting Friday. The union said the strike was being called because of a deadlock in contract negotiations. Candice Johnson, a spokeswoman for the Communications Workers of America, Johnson said the strike would begin at one minute after midnight local time Friday morning. She said workers will return to their positions at 12-oh-one- a-m Tuesday. S-B-C spokesman Selim Bingol said the company did not have immediate comment about the strike. C-W-A president Morton Bahr said the union opted for a short strike to get its message across without doing too much harm to S-B-C. Bahr said a prolonged strike could cost the company some major customers and do significant damage to the company. A strike would likely affect local phone service in S-B-C`s 13-state coverage area, which includes Arkansas, Texas, California, Illinois, Michigan, Ohio and Connecticut. It would be the CWA`s first strike against S-B-C since a three-week action in 1983. The union has criticized the company for its positions on wages, health care costs and job security.