A synth control bus, similar in concept to MIDI, developed by Roland around 1979. At around that time, Roland introduced its first line of digital hardware sequencers, and equipped them with DCB outputs. Several synths were produced with DCB inputs, including some versions of the Jupiter-8. When Roland and Sequential Circuits were devising the original MIDI specification in 1981, Roland put forth the DCB bus as the proposed MIDI standard; DCB was capable of transmitting data much faster than the standard eventually adopted. However, DCB required bulky cables and was more expensive to produce circuitry for, so it was not adopted. Later, Roland produced retrofit kits which added MIDI capability to synths and sequencers with DCB interfaces.