Self-contained batteries are designed to allow the devices to continue pinging for about 30 days, said Pat Cariseo, a spokesman for the National Transportation Safety Board. Officials said yesterday that they are moving on to sonar to try to find the boxes after the Navy's locator device failed to detect signals. The black boxes are actually painted orange, so they may be located during visual searches. The pingers don't always lead searchers to the recorders. Sometimes the crash's force separates them from the black box, Cariseo said.
Location can also hamper the search.