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boxes, and the Australian official in charge of the search expressed hope Wednesday that the plane's wreckage will soon be found.
• Angus Houston, the head of a joint agency coordinating the search for the missing plane in the southern Indian Ocean, said that the Australian navy's Ocean Shield picked up the two signals on Tuesday, and that an analysis of two sounds detected in the same area last week showed they were consistent with a plane's black boxes.
• "I'm now optimistic that we will find the aircraft, or what is left of the aircraft, in the not-too-distant future -- but we haven't found it yet, because this is a very challenging business," Houston said at a news conference in Perth, the hub for the search operation.
• The Ocean Shield first detected underwater sounds on Saturday before losing them, but managed to pick them up again on Tuesday, Houston said. The ship is equipped with a U.S. Navy towed pinger locator that is designed to detect signals from a plane's two black boxes -- the flight data recorder and cockpit voice recorder.
• A data analysis of the signals heard Saturday determined they were distinct, clear and pulsed consistently -- indicating they were coming from a plane's black box, Houston said.
• ___

• PERTH, Australia (AP) -- Searchers looking for the missing Malaysia Airlines plane have discovered new signals consistent with those emitted by so-called black boxes in the Indian Ocean, but they do not want to send a submersible down yet to look for the plane. For now, they will continue to use the towed pinger locator to get a better fix on the location. Here's why:
• ___
• THE TOWED PINGER LOCATOR
• The Australian Navy vessel Ocean Shield picked up the signals using a U.S. Navy device called a towed pinger locator. It's essentially a long cable with a listening device, or hydrophone, attached to the end. It's pulled behind the boat at a depth of 3 kilometers (1.9 miles).
• The pinger locator is designed to detect signals at a range of 1.8 kilometers (1.2 miles), indicating it would need to be almost on top of the black boxes -- the flight data and voice recorders -- to detect them if they were on the ocean floor, which is 4.5 kilometers (3 miles) under the surface. However, the latest detections indicate

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