Metro management on Thursday told board members about concerns that have been raised regarding emergency intercoms on trains, and explained what and when they knew about problems with the systems.

Concerns about how well the intercoms work came up after an incident last month where riders were unable to reach the train operator as a fight broke out on a Red Line train.

Then Wednesday evening, some riders reported they couldn’t get intercoms to work on trains that were delayed after a brake problem on a train near Clarendon caused delays of more than two hours for commuters.

At Thursday’s safety and security committee meeting, Metro officials said the problems with the intercoms happen when 1000 series rail car are combined with 4000 or 6000 series cars. Officials said there also are problems with intercom systems on it 2000 and 3000 series rail cars. On the 2000s and 3000s, the problem involves a false signal being sent out from the intercom to the train operator cab.

Rob Troup, Metro’s director of rail operations, said parts on circuit boards of the 6000 series cars have been fixed. He said another fix for the 4000 series cars is being tested and should be put in “full scale production” in the coming months.

The 6000 series intercom problem was first realized in late 2009. Officials said the  problem was intermittent and that new digital control panels “were to be put in on the 1000 [series rail cars], but subsequent testing revealed that wouldn’t work,” Troup said.

The discovery followed the deadly Red Line crash at Fort Totten that killed nine people and injured dozens in June 2009, and Metro officials said they prioritized other safety work  based on recommendations from the National Transportation Safety Board.

Among the safety improvements Metro said it prioritized were fixing door problems and  replacing the oldest rail cars — the 1000s, which were involved in the Red Line crash.

“People were making reasonable prioritization decisions,” Metro General Manager Richard Sarles said. He said there were “critical safety items from the NTSB that had to be addressed” and said those fixes were “very high priority items” that were “clearly higher and more critical than this,” referring to the intercom problems.

“Nothing’s ever perfect,” Sarles said. “The focus was on the most safety priority item at the time. Eventually it was picked up and we addressed this item again.”

In reading from a statement to the board, Troup said, “In the latter part of 2012 engineering renewed efforts to determine the cause of inconsistencies in intercom performance.”

In April, he said “engineering investigation, design changes and testing were progressed to where we understood systemic issues and permanent engineering modification instructions were approved.”

Since then, officials said they also have “reevaluated daily safety tests” of intercoms and done random testing for “intercom checks.”

“Once we identified the failure [of the intercoms] as a system wide failure it was and is being treated as a serious issue,” said Jim Dougherty, Metro’s chief safety officer.

Troup said officials also discovered that some train operators were “disabling” the intercoms themselves because of the “noise and feedback” they received.

He said operators have since been directed to not disable the intercoms.