It is a depth finder/fish finder. It has three option....worn like a watch, fishin pole mounted and/or regular type led Disply. The "transducer" is wireless. Hummingbird calls it the RSS (remote Sonar Sensor). You attach the RSS to the fishing line like a bait and throw it out In the water. It then transmittal data via RF and the receiver processes the info just like a typical depth finder.

The issues I had...
1) up to ten minutes to latch/connect each time I used it.
2) slow refresh rate
3) random loss in signal, mostly after each cast
4) put it in my pool and it said it was 11ft. My pools is 7ft at deep end and it was in the middle

Know 1, agreed. However, RF technology has been around for a long time. I would expect for 99.00 allot more. I use lots of RF devices all on different freqs and never experience that kind of data loss. Given the size of hummingbird I would expect a bit more. The performance I experienced is one of a prototype.

Chuck