Communications room. Patch panel and wires in an office communications room. The blue and yellow wires carry voice and computer data to and from a network of telephones and computers. The colour- coding is yellow for telephone data, and blue for computer data. The numbers on the panel show which plug corresponds to which telephone or computer. The wires connect the panel to the black boxes (lower right). These are called routers and switches, and they transfer data from one network to another. This Ethernet technology is a vital part of the technology of the internet.