I heard of a guy who knew a guy who's cousins nephew built one for catfish. Since these devices are illigal, that was purposefully vague, but it was not me! Anyhoo, it consisted of a 555 timer delivering a square wave into the base of a high current transistor. I don't remember if it was wired as an emitter follower or if the output came off of the collector, but it did a high current capable 12 volt amplitude square wave. Memory fails me once again, but 200 sounds familar. So it was either 200mS for the time or 200 hertz. Sorry so vague, but as I said, I didn't build it.
