Cabling that consists of a glass core which is surrounded by a number of layers of protective materials. It is a light conducting medium which, consequently, does not suffer from electrical interference. It is normally used in environments where electrical interference is high; it is also used to connect buildings together because it is highly resistant to external weather conditions. Fibre optic cable is faster than other cabling such as coaxial cable and is often used for high bandwidth applications such as video conferencing. The principle of operation of such cabling is simple: light is generated at one end and is pulsed in binary signals down the glass towards a detector at the end of the cable which converts the light pulses to digital signals. Fibre optic transmission lines where the light continually bounces off the central core is known as multimode fibre; if it travels in a straight line then it is known as single-mode fibre.