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• n  a pulse generator used for echo sounding in sonar

• The electronic homing pinger was reportedly missing from one box and the pinger on the other was operational but apparently shielded, complicating the recovery effort.
• Three hundred feet up its cable it carried a "pinger," whose sound could be detected by the Chain four miles above.
• Weekends, he uses his own underwater sonic pinger for a scientist's hobby: probing Boston's Charles River for an 800-year-old Viking ship that he believes may lie on the bottom.

News & Articles

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• N.H. Fishermen Double Down On New Generation of Pingers To Save Migratory Porpoise
  Gillnet fishermen in New Hampshire will be using new electronic devices to prevent trapping harbor porpoise in their nets. Last year, the fishermen were penalized for problems with the devices known as pingers.  And this year’s purchase marks the largest mammal catch prevention initiative of its kind.
  June 9, 2013 - New Hampshire Public Radio