SAN FRANCISCO (CBS SF) — A device which looks like an old-time train whistle connected to a locked box – and mysteriously set up on a downtown San Francisco street corner – has been determined to be part of the Department of Homeland Security’s Super Bowl security preparations.

According to the department, it’s an air sampling device used in the BioWatch program; a national system for detecting a biological attack.

The monitor is connected to a pole which connects to a large, metal box with wheels. The box is padlocked and has a yellow tag on it with a stern warning from Homeland Security: “DO NOT UNPLUG!!!”

The BioWatch program has had its critics. According to a 2014 LA Times article, the program has cost taxpayers more than a billion dollars so far, and has been deemed so ineffective that a plan to launch a new, improved system was scuttled.

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The cancellation of the “Generation 3” acquisition was made at the direction of Homeland Security Secretary Jeh Johnson, according to a memorandum circulated by Michael V. Walter, the BioWatch program manager.

Homeland Security officials earlier had told companies interested in supplying the technology that it would spend $3.1 billion for it during the first five years of operation.

To date, the overall BioWatch program has cost taxpayers more than $1.1 billion.

Walter said in his memo that the department “remains committed to the BioWatch program and the importance of improving our early warning and detection technologies.”

Jeff Harp, a security analyst for KPIX 5 and a retired FBI assistant special agent-in-charge, said the devices are better than nothing. “They’re keeping you safer than if you didn’t have them,” he says.

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As for the day-and-a-half it can take to detect a biological agent, Harp said that’s still well within a window for effective treatment.

“If you or I had anthrax you would want to know immediately. Sometimes that isn’t always going to happen,” said Harp. “They’re looking at a 12-to-36 hour turnaround on the samples, but that still is enough time to get the prophylactic treatment if it was anthrax.

“If you go to drive a big nail in the ground and you have a small hammer … but you still have to drive that nail in the ground, then you’re going to use what tool you have to get that job done. Obviously, a bigger hammer is better to drive the nail … So it’s just one tool in the toolbox that they can use for early detection.”

A Homeland Security spokesman, S.Y. Lee, said the cancellation reflected a commitment to “cost-effective acquisition without compromising our security.”

Last year, the department was addressing the challenges faced by the BioWatch program and was committed to the program’s role as part of a layered and integrated approach to the nation’s biodefense and surveillance systems.