Otis made an operator which had a small geared machine on top of the car. The machine lifted a weight on the side of the car, like a retiring cam. This weight connected with a lever system that replaced the broken arm style opener on the hoistway doors. When the weight was lifted, the HW doors were closed and when the weight was lowered, the HW doors opened. I want to say it was an A, B, or AB style operator. I haven't seen one in about 20 years, and the last ones I worked on was about 40 years ago. They used them in a lot of Department stores and a lot of Federal buildings. It was an expensive option.
