Abstract: A communication IC (11a) in an AV controller (1) periodically notifies plural slave apparatuses (e.g., a CD player (3), a radio (5), and an amplifier (7)) of a system state command containing a system state in which states of all the plural slave apparatuses are managed in a lump. CPUs (13a to 13d) of the slave apparatuses determine whether or not the current apparatus state of the corresponding slave apparatus coincides with the system state in the system state command from the AV controller. If the current own apparatus state does not coincide with the system state in the system state command, the current own apparatus state is made coincident with the system state command.

Abstract: In a ring network system in which a plurality of devices each having a first communication IC are connected in a ring-like manner by a transmission line to mutually effect transmission and reception of data among the devices, an rack unit is disposed between two adjacent ones of the plurality of devices, the rack unit and the plurality of devices are connected in the ring-like manner by the transmission line, wherein the rack unit has a plurality of device inserting slots in which a plurality of additional devices are installed and which are provided in correspondence with the plurality of additional devices, and a second communication IC for controlling data communication among the plurality of additional devices installed in the plurality of device inserting slots and for controlling data communication between the additional device and the network device.

Abstract: A multiplex transmission apparatus is constructed with a plurality of nodes being connected to a multiplex transmission path. Each node has a multiplex transmission module for making multiplex communication with another node, a reception circuit connected to the multiplex transmission, and a micro-controller. The multiplex transmission apparatus has as its operation mode a multiplex communication mode in which each node performs its multiplex transmission and a sleep mode in which a multiplex transmission module is kept inoperative.

Abstract: A master node and slave nodes which are connected in a ring-like manner transmit commands in one direction, each of the nodes transmits a state monitoring command for monitoring the operational state of the network to its immediate upstream-side node, and the operational state of the network is monitored by a response from the immediate upstream-side node with respect to the state monitoring command. A traffic monitoring unit monitors the amount of traffic in the network and determines whether or not the amount of traffic is less than a predetermined value, and a start-command transmitting unit transmits a start command for instructing the start of transmission of the state monitoring command to each of the slave nodes if it is determined that the amount of traffic is less than the predetermined value.

Abstract: In each control node connected to an optical multiplex transmission path, a light receiving portion operates due to supply of a power source and receives an optical signal from another control node. A mode changing-over portion alternately changes over a multiplex communication mode and a sleep mode every prescribed period of time. A light receiving power source control portion and a first switch have alternately repeated therein a power source supply time length corresponding substantially to the multiplex communication mode during which a power source is supplied and a power source non-supply time length corresponding substantially to the sleep mode during which no power source is supplied, and thereby produces a power source supply pulse signal in which the duty ratio between the power source supply time length and the power source non-supply time length is preset and supplies this power source supply pulse signal to the light receiving portion.

Abstract: In a normal operation mode, paths in a communication IC are controlled so that data received from a transmission line and addressed to this node is captured into a digital signal processor of the node and so that source data is sent from the node to the transmission line. In a test mode, the paths in the communication IC are controlled so that data received at a second input terminal of the communication IC is output from a first output terminal. In the test mode, comparison source data from a comparison source data unit is sent to the second input terminal via a first multiplexer. An error detection unit compares the comparison source data with output data, which is output from the first output terminal of the communication IC in response to the comparison source data, to detect errors in the communication IC.