Pinger

A pinger is a small acoustic transmitter that emits short repetitive pulses for tracking, positioning, or deterrence. Acoustic-release and transponder pingers locate moored instruments and tow bodies; pinger-based USBL and LBL systems position underwater vehicles by ranging on the pulses. In fisheries, acoustic deterrent pingers near 10 kHz, with source levels around 130 to 150 dB, are fitted to gillnets to warn off harbor porpoises and dolphins and cut bycatch, a use mandated in several fisheries. Locator pingers on aircraft recorders are a related design, emitting at 37.5 kHz to aid underwater search.