They're mostly embarrassing mistakes that only take a split second, but end up eating precious time and costing police departments thousands of dollars every year: The 911 hangup calls.

Last year in Ramsey County there were 5,735 calls to 911 that ended with the caller hanging up before a dispatcher could answer. Dispatchers are required to call back, and when there's no answer, they must send an officer or two to the address to ensure there is no emergency.

The calls -- mostly accidental -- tie up officers and result in incalculable costs, said east metro law enforcement officials.

"What we see a lot of times is that people out of embarrassment won't answer when the dispatcher calls back," said Maplewood Police Chief David Thomalla. "In a lot of cases, we have to verify that there are no problems. It's a huge financial impact."

The exact dollar cost isn't tracked by individual departments because the time officers spend responding to and clearing a 911 hangup call is built into regular work hours, but Thomalla said it easily costs his 53-officer department tens of thousands of dollars every year.

The Ramsey County Emergency Communications Center dispatches for St. Paul and all cities in Ramsey County, and receives about 300,000 emergency calls a year. The 911 hangups account for only about 2 percent of that total, but those few thousands calls keep officers from other calls, authorities said.

"It does use our resources," said officer John Keating, a St. Paul police spokesman. "That's ... keeping [officers] available for other things going on in the city."

Most often, people accidentally dial 911, hit it on speed dial, start to report an incident and then stop when someone else calls, or sometimes it's just curious youngsters who get too handsy with the phone.

Sometimes, however, it's a real emergency -- maybe someone who can't speak because of a medical issue or a domestic abuse victim who is interrupted by the abuser.

If the call is an accident, authorities have one piece of advice: Stay on the line and explain the mistake.

"It's almost impossible to hang up fast enough to prevent that call from being routed to the dispatcher," said Scott Williams, director of the county's Emergency Communications Center. "It makes our job easier if you stay on the line. We won't yell at you."

Last year, St. Paul police responded to 3,735 911 hangup calls, most of them accidental.

"There's certainly a possibility that there could be any type of emergency at an address, so it's important for us to respond," said Keating, adding that residents shouldn't hesitate to call 911 if they do need help.

The Communications Center is in the early stages of creating a public service announcement to be shown on local cable-access TV that will address a number of issues involving its services and challenges, including proper etiquette for people who accidentally dial those three squad-summoning numbers.

Williams hopes the video will debut later this year. Until then, he had one plea: "Just say you called 911, or you might have a police officer show up at your door."

Chao Xiong • 612-270-4708 Follow Chao on Twitter: @ChaoStrib