Germanium is used as a semiconductor material. It is commonly used, together with silicon, in high speed integrated circuits for improved performance. There is some work being done to replace silicon with germanium in miniaturized chips. It is also used in fluorescent lamps and some LEDs. Some guitar effects pedals contain germanium transistors to produce a distinctive fuzz distortion tone. It can be used in solar panels. In fact, the Mars Exploration Rovers contain germanium in their solar cells. Germanium is combined with oxygen for use in camera lenses and microscopy. It is also used in the core of optical fiber cables. It is also used in thermal imaging applications for military and fire fighting use. It is also used in airport screening, and other applications, to detect sources of radiation. There are some suggestions that it can be used to support the immune system of cancer patients, but this is still being debated. The FCC now lists germanium as a potential health hazard when used as nutritional supplement.