An electronic device configured for communication on a clock synchronous bi-directional point-to-point two-wire communications bus, comprising: first circuitry arranged to: communicate with at least one upstream device over a bi-directional point-to-point two-wire communication bus, wherein the at least one upstream device includes a master device, periodically receive a downstream transmission communicated downstream on the two-wire communication bus from the master device, the downstream transmission comprising a synchronization control frame that occurs at the beginning of the downstream transmission and a plurality of first data blocks that occur subsequent to the synchronization control frame, each first data block containing data for a slave device actuator, and transmit an upstream transmission on the two-wire communication bus, wherein the upstream transmission originates at the last downstream device on the communication bus, the upstream transmission comprising a synchronization response frame that occurs at the beginning of the upstream transmission and a plurality of second data blocks that occur subsequent to the synchronization response frame, each second data block containing data generated by a slave device sensor; second circuitry arranged to derive timing information from the synchronization control frame; and third circuitry arranged to: transmit the downstream transmission downstream to a downstream device, and receive the upstream transmission from the downstream device. first circuitry arranged to: communicate with at least one upstream device over a bi-directional point-to-point two-wire communication bus, wherein the at least one upstream device includes a master device, periodically receive a downstream transmission communicated downstream on the two-wire communication bus from the master device, the downstream transmission comprising a synchronization control frame that occurs at the beginning of the downstream transmission and a plurality of first data blocks that occur subsequent to the synchronization control frame, each first data block containing data for a slave device actuator, and transmit an upstream transmission on the two-wire communication bus, wherein the upstream transmission originates at the last downstream device on the communication bus, the upstream transmission comprising a synchronization response frame that occurs at the beginning of the upstream transmission and a plurality of second data blocks that occur subsequent to the synchronization response frame, each second data block containing data generated by a slave device sensor; communicate with at least one upstream device over a bi-directional point-to-point two-wire communication bus, wherein the at least one upstream device includes a master device, periodically receive a downstream transmission communicated downstream on the two-wire communication bus from the master device, the downstream transmission comprising a synchronization control frame that occurs at the beginning of the downstream transmission and a plurality of first data blocks that occur subsequent to the synchronization control frame, each first data block containing data for a slave device actuator, and transmit an upstream transmission on the two-wire communication bus, wherein the upstream transmission originates at the last downstream device on the communication bus, the upstream transmission comprising a synchronization response frame that occurs at the beginning of the upstream transmission and a plurality of second data blocks that occur subsequent to the synchronization response frame, each second data block containing data generated by a slave device sensor; second circuitry arranged to derive timing information from the synchronization control frame; and third circuitry arranged to: transmit the downstream transmission downstream to a downstream device, and receive the upstream transmission from the downstream device. transmit the downstream transmission downstream to a downstream device, and receive the upstream transmission from the downstream device.