Sporadic periods of overflowing circuits have frustrated students trying to make long-distance calls since Friday.

"For short periods of time on Friday, Sunday and Monday, students heard a fast busy signal meaning that the circuits are full," said Robert F. Grenier, manager of the Harvard Student Telephone Office (HSTO).

Technicians are still trying to locate the problem.

"People at Bell Atlantic, MCI and AT&T [carriers for the Harvard community] have been working on it," Grenier said.

"It's affected the administrative lines as well," he said.

Students expressed frustration at being unable to call outside the Harvard area.

"I tried four times to get through but all I got was a fast busy signal. I thought my line had been disconnected," said Jennifer Y. Cho '01.

Grenier added that the random, intermittent nature of the clogged circuits makes it harder to find a solution.

"If the lines were consistently busy, the problem would be easier to isolate and track down," Grenier said.

The switch which serves the Harvard community also serves parts of Cambridge.

This means that the problem could be impacting other Cambridge residents.

Grenier said student PAC numbers are not linked to the overflowing circuits.

Grenier said that in his five years at HSTO he has never received complaints of this nature.

"This is very unusual. We understand that this is a problem that requires immediate attention," Grenier said.

"Extensive research on the circuits is going on right now," he said.