In a digital telecommunication service, the original source is transformed into and transmitted as a series of digits in binary code (i.e. 0s or 1s). Voice, text, image or data are all equally capable of being coded as a digital signal, so that a single network can handle all four forms of transmission (multimedia). The string of binary digits can be abbreviated and then re-expanded on arrival, thus economising transmission capacity. Different strings of binary digits can be interleaved and transmitted together, thus permitting several separate conversations on a single line (multiplexing). The string of digits can be encrypted prior to transmission, to ensure a high level of information security and privacy. Through digitalization, even a severely degraded transmission can be reconstructed to reproduce perfectly the original source.