Campbell Aird's right arm was amputated in 1982 after doctors diagnosed muscular cancer. His bionic arm is called the Edinburgh Modular Arm System, and is packed with microchips, position-control circuits, miniature motors, gears, and pulleys. It rotates at the shoulder, bends at the elbow, rotates and twists at the wrist, and can grip using artificial fingers. Campbell wears a cap containing an array of microsensors that pick up the electrical pulses his brain is still sending to his absent arm muscles. These pulses then control each movement of his "new" arm.