Most members of the Harvard community lost their phone service for several minutes yesterday due to a computer failure which affected more than 21,000 Cambridge residents.

The affected phones could receive calls but not make them

An official at the Cambridge branch of New England Bell said yesterday that the computer breakdown affected no other communities and may have been caused accidentally by technicians installing new phone equipment.

Jackie Jung, Bell Service public relations manager, said the computer damage occurred at 3:30 p.m. and was repaired within six minutes After the repair, however, a glut of outgoing phone calls overloaded the computer's switchboard and prevented the phone company from restoring full service for an hour and a half.

"Especially in a busy area like Cambridge," Jung said, "people's first reaction to a loss of phone service is to continuously try to make calls. Our equipment is made to handle a 'normal' capacity and cannot transfer all the additional calls."

Jung said that 21,000 of the 42,000 phones in Cambridge broke down, including all phones on the 495 and 498 exchanges.

An official at the Harvard Phone Office estimated that similar Bell System breakdowns affect university telephones about once a year.