The D-TAR Sadducer is an under-saddle transducer which uses six discrete piezo crystals, allowing one for each string of a steel string, or nylon string acoustic guitar. Not only is it a high-output pickup, but it doesn’t require a preamp, which means no batteries required.
Incidentally, D-TAR stands for Duncan Turner Acoustic Research, which is a partnership between Seymour Duncan and Rick Turner, who co-founded Alembic, Highlander Musical Audio and the Rick Turner Guitar Company.