Navico xSonic TM185M Transom Mount Transducer [000-13998-001]xSonic TM185M Transom Mount Transducer As Chirp continues to redefine recreational fishing, AIRMAR has expanded the lineup of single band transducers to satisfy the growing demand for this game changing technology. The TM185M, an economical Chirp transducer, is designed for offshore fishing and freshwater anglers. Operating at a frequency range of 85 135 kHz, these transducers reveal fish in shallow, murky waters at medium depths (up to 1,500 feet*)