Digital systems from Sennheiser, Sony, Shure, Zaxcom, AKG and MIPRO use the same UHF frequencies used by analogue FM systems for transmission of a digital signal at a fixed bit rate. These systems encode an RF carrier with one channel, or in some cases two channels, of digital audio. Only the Sennheiser Digital 9000 system, introduced in 2013, is currently capable of transmitting full-bandwidth, uncompressed, digital audio in the same 200 kHz bandwidth UHF channels that were used by analogue FM systems.[15] The advantages offered by purely digital systems include low noise, low distortion, the opportunity for encryption, and enhanced transmission reliability.