Abstract: A communication system includes: a first signal line; a second signal line; a first signal line selection portion and a second signal line selection portion for selecting either one of the first signal line and the second signal line so as to be effective as the serial data; and a signal control portion for outputting a signal direction switching signal for controlling a selecting operation. The first signal line selection portion includes a first OR circuit and a first three-state buffer circuit provided on the first signal line, and a first buffer provided on the second signal line, and the second signal line selection portion includes a second OR circuit and a second three-state buffer circuit provided on the second signal line, a second buffer provided on the first signal line, and an inverter circuit provided between a terminal of the signal control portion and the second OR circuit.

Abstract: A bus node, a communication unit, which can be coupled for communication to at least data line of a bus; having a bus node controller, which is coupled operationally to the communication unit; and having an identification unit, which has a quadripole connectable, instead of a direct connection, between an IDT input and an IDT output for an identification line and vice versa, the quadripole being configured such that upon a serial interconnection of a first bus node with at least one second bus node for the bus node controller, the position of the first bus node is identifiable on the basis of a comparison of the voltage at the IDT input with a predetermined threshold value, regardless of the number of second bus nodes.

Abstract: Provided is a digital-image transmission apparatus including a transmitting unit connected to a host device and a receiving unit connected to a display device. The transmitting unit includes a host-side additional-communication control unit that controls additional communication for digital image transmission. The host-side additional-5 communication control unit performs communication with an external device to diagnose an operation state of the transmitting unit, transmit a diagnosis result to the external device, and control an operation of the transmitting unit.

Abstract: An expansion module for a PLC, used in such a manner that at least one expansion module is sequentially connected to a basic unit in order to exchange massive data at high speed by using USB communication, is provided. Each of the expansion module includes a USB hub and a USB device, and is allocated with an exchange number from a USB host of the basic unit by activating the USB device according to input of a trigger signal. In addition, whether the USB hub is to be used is determined by deciding whether the expansion through the USB hub is required according to the allocated exchange number. Thus, a user needs only to arrange each of the expansion modules by a designation.