Spacing the brand new changes like this inhibits a keen operator out of seeking to in order to force each other keys down which have one-hand otherwise object. You to definitely defense approach that makes use of the brand new interlock try a white curtain, that’s an enthusiastic infrared light-beam you to definitely reveals the brand new mesh if someone disrupts one area of the beam. The fresh productivity of one’s light curtain is attached to the mesh terminal on the hipot examiner.