A low-voltage, low-power, synchronous, bidirectional, time-multiplexed,
serial communication, scalable system bus carrying a number of signals
over a fewer number of wires between a master device and peripheral
devices or between peripheral devices. One of the wires carries a
composite digital signal that includes a data signal and a synchronizing
signal, though other combinations are contemplated. The system bus can
support more peripheral devices than there are available time slots, and
supports interrupt polling and servicing. In addition, peripheral devices
that include an electro-mechanical or electro-acoustical component
connected to the system bus can also communicate directly to each other
without using the system bus. The system bus can be implemented in low
voltage, low power devices, including listening devices such as hearing
instruments and headsets, portable telephones, and personal digital
assistants.