Great introduction to the industry standard for point-to-point and multipoint serial communication.

Great intro to the industry standard for infra-red communication. Includes hardware, components, protocols, links, etc.

In this article you will find a functional description of RS-232 signals.

IRQ's and COM devices, 8250 and Compatible UARTs...

Description of Basic Transfer Protocols used in Ethernet

In this article you will learn about Fiber optic cable & UTP categories

Active parts are main stuffs for running network. Network Topology describes the way network cabling is laid out. This doesn't mean the physical layout (how it loops through walls and floors), but how the logical layout looks when viewed in a simplified diagram.

For applications like this embededd systems, microservers, automatization, industry applications, IP telephony, firewall or router are suitable use the devices with Linux operating system and two Ethernet connectors. This article describe such the device. It's the Small Linux Device - SLD PXA 255 with the DIMM BASE BOARD. The main benefits are low price, lesser dimension, lower consumption and higher reliability.