Brass knuckles are far to nice for that guy I was thinking more of this.
The Tucker telephone was a torture device invented by a physician at the Tucker State Prison Farm in Arkansas in the 1960s. It incorporated an old-fashioned crank telephone wired to battery cells. A ground wire was wrapped around the big toe of a prisoner and the hot wire was wrapped around the genitals. The crank was then turned, inflicting a horrible electric shock on the victim. This could – and did – lead to cases of organ damage and insanity. Its use was confirmed up until 1968, and there are also reports from Vietnam veterans that it was used on Vietcong prisoners using manipulated field telephones.