They refer to a pulley system around a toilet and over a door in Todd's flat.

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The knobs are connected to a pulley system, which moves a brass stylus along an X-Y axis.

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This kind of transmission uses a pulley system to simulate gears and is usually more efficient than traditional automatic transmissions.

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The couple also found no evidence of a pulley system: there were no pulleys or holes in the ceramic walls in the bathroom, Mary Todd said.

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