"Fruit machine" is a jocular term for a device developed in Canada that was supposed to be able to identify homosexual people, or "fruits". The subjects were made to view pornography, and the device measured the pupils of the eyes, perspiration, and pulse for a supposed erotic response.
The fruit machine was employed in Canada in the 1950s and 1960s during a campaign to eliminate all homosexuals from the civil service, the Royal Canadian Mounted Police (RCMP), and the military. A substantial number of workers did lose their jobs. Although funding for the "fruit machine" project was cut off in the late 1960s, the investigations continued, and the RCMP collected files on over 9,000 suspected homosexuals.
The chair was like one from a dentist's office. It had a pulley with a camera going towards the pupils. There was a black box in front of it that showed pictures. The pictures ranged from the mundane to sexually explicit photos of men and women.
People were told the machine was to rate stress. After knowledge of its real purpose became widespread, few people volunteered for it.
There is no evidence of scientific validity of the machine.