The unit, not much bigger than a cell phone, was developed after a May 1986 hiking tragedy that claimed the lives of nine students and staff from the Oregon Episcopal School who were trapped by bad weather during an annual hike.
The units send a radio signal that search teams can use to triangulate the rough coordinates of lost climbers. The device is sewn into a thick strap and worn across the torso or inside a backpack. When activated, it sends out a radio signal. Searchers on Mount Hood are equipped with special receivers programmed to pick up the signal, which can extend as far as five miles but is affected by natural obstructions such as cliffs.
"It's pretty much line of sight," said veteran climber Steve Rollins of Portland Mountain Rescue. "If we can see it, we can receive it."
But someone still has to call authorities to alert them of the missing person, or no one will look for the signal, Rollins said.
"Activating a mountain locator unit does not activate a rescue for you," he said. "And it certainly doesn't guarantee that we can get to you."
The units became a subject of debate after three other climbers -- Brian Hall, Jerry "Nikko" Cooke and Kelly James -- went missing last year while climbing Mount Hood. Their fate became a national story as blizzardlike conditions pinned searchers near the timberline for days.
None of the men had an MLU, though James had a cell phone that he used to call his family from a snow cave near the summit where his body was found. All three died on the mountain.
Somerescue groups and climbers are wary of making the units mandatory. "Sometimes it gives people a false sense of security," said Todd Wells, a searcher with the Hood River Crag Rats.
Wells also questioned the MLU's effectiveness. He was one of the rescuers using a receiver Sunday to track the signal emitted from the party's MLU. "It was like a needle in a haystack," he said.
Other distress beacons are also available, including avalanche transceivers that can send and receive signals.
More recently, personal locator beacons have become available. They're similar to those carried by ships or airplanes, and communicate with satellites. They send out a distress signal along with a location, but cost about $500.
At minimum, experts advise people heading into the backcountry to a carry a cell phone, compass, maps and a global positioning system unit. And they should know how to use them.
