Silence on the Wire

A Nonelectric Computer

Moving from a set of theoretical operations spawned by the world of pure mathematics to a device that can moderate water flow, torques, or electrical signals in a way that mimics one of the logic operators appears to be a difficult task—but it isn’t.

Figure 2-1 shows a trivial gear set mechanism that implements NOR functionality using torque-based logic. The “output” wheel at idle represents state 0; when a torque is applied to the wheel, its state is 1. The device transmits torque from an external source to the output only if no torque is applied to two control “input” wheels. In theory, there is no need for an external source of energy, and the design could be simpler; in practice, however, friction and other problems would ...