I Should Use Innuendo Here

Oh sure, they look alike; one is AC (top) the other DC. One of the species, Brachyhypopomus bennetti, has a large electric organ and a short fat tail and produces direct current, or a monophasic, signal; the other, Brachyhypopomus walteri, has a more typical electric organ, a long thin tail and an alternating current, or biphasic signal.

(from the August 28 edition of ZooKeys)