There are a number of implementations of the physical layer.
Network devices allow a wide range of connectivity options.
Some networks are well defined using the OSI model, where cables, bridges, routers, servers, modems, and PCs are easily identified. Sometimes only a few devices are linked together in some kind of proprietary network, or where the network services are bundled in a black-box fashion with the device. The DCE is the component actually doing the communicating, or, performing the functions of the generator and receiver discussed in the standards. The interfaces between DTE and DCE can be categorized by mechanical, electrical, functional, and procedural aspects. Mechanical specifications define types of connectors and numbers of pins.