A bus design is said to be proprietary if the design is owned by a private company
and not available for use by other companies (i.e., covered by a patent). The alternative
to a proprietary bus is known as a standardized bus, which means the specifications are
available. Because they permit equipment from two or more vendors to communicate
and interoperate, standardized buses allow a computer system to contain devices from
multiple vendors. Of course, a bus standard must specify all the details needed to construct
hardware, including the exact electrical specifications (e.g., voltages), timing of
signals, and the encoding used for data. Furthermore, to ensure correctness, each device
that attaches to the bus must implement the standard precisely.