Radio Mouth Brace
This brace is a simple and easy-to-use tracking device. The radio transmitter is held on a circuit board printed over the top of the brace, so that it lies against the roof of the mouth. The metal loops which hold it in place act as an aerial. When it is worn, the brace transmits a steady and powerful signal which is constantly monitored by MI6’s network of radio towers. Each tower analyses the direction and strength of the signal, and by putting this information together the location of the wearer can be pinpointed. The accuracy of the system depends on the amount of information available, but it is usually as close as thirty metres. A tiny switch built into the underside of the brace changes the frequency of the radio signal being produced. This is often used as a distress call. The brace operates on kinetic power, in the same way as some modern watches. At the back of the device, in a hollow moulded to the roof of the wearer’s mouth, is a small, flat box containing a capacitor, a small weight and a microgenerator. As the wearer’s head moves, the weight moves back and forth, causing the generator to spin. This produces enough current to keep the capacitor charged and the radio signal transmitting.