There is disclosed a protocol which can use the existing network bandwidth limitations for transmission during at least the
bus contention period after which the remaining portion of the data should be collision-free but allow for a choice of signalling rate within the frame after that
bus contention period for the
payload data to be transmitted, thus allowing the use of a different
data rate in parts of a frame. Additionally there is disclosed advantages to be gained by making best use of available but otherwise not used network bandwidth capability at different parts of the transmission of a frame, such that the protocol enhancement should be compatible with existing installed devices and associated controllable arrangements, so that a
system existing in a network can be upgraded, by adding one or more of the devices and associated controllable arrangements which can transmit and receive both the original standard (typically lower)
data rate as well as the newer (typically higher)
data rate transmissions, at the convenience of the owner of the network without a
cost burden associated with replacement or the upgrading of all existing devices or associated controllable arrangements.