on a radio station in Rome. One could typically hear a radio station on a foxhole radio if they lived twenty five or thirty miles away. In 1942, Lieutenant Colonel R. G. Wells—a prisoner of war in Japan—built a foxhole radio to get news about the international situation. "The whole POW camp craved news", according to Wells. Richard Lucas, a POW in Vietnam, constructed a radio in camp and built his own earphones. Designs and operation Foxhole radios consisted of a wire aerial, a coil of wire serving as inductor, headphones, and some sort of improvised diode detector to rectify the signal. Detectors consisted of an electrical contact between two different conductors with a semiconducting film of corrosion between them. They were devised from various common objects. One common type was made from an oxidized razor blade (rusty or flamed) with a pencil lead pressed against the blade with a safety pin. The oxide layer on the blade and the point contact of the pencil lead form a semiconductor Schottky diode and only allow current to pass in one direction. Only certain sites on the blade acted as diodes, so the soldier moved the pencil lead around on the surface until the radio station was heard in the earphones. Another detector design was a battery carbon resting across the edges of two vertical razor blades, based on the 1879 "microphone" detector of David Edward Hughes. The aerial is connected to the grounded inductor. The coil has an internal parasitic capacitance which, along with the capacitance of the antenna forms a resonant circuit (tuned circuit) with the inductance of the coil, resonating at a specific resonant frequency. The coil has a high impedance at its resonant frequency, and passes radio signals from the antenna at that frequency along to the detector, while conducting signals at all other frequencies to ground. By varying the inductance with a sliding contact arm, a commercial crystal radio can be tuned to receive different frequencies. Most of these wartime sets did not have a sliding contact and were only built to receive one frequency, the frequency of the nearest broadcast station. The detector and earphones were connected in series across the coil, which applied the radio signal of the received radio station. The detector acted as a rectifier, allowing current to flow through it in only one direction. It rectified the oscillating radio carrier wave, extracting