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.
Electrical specifications define line voltages and waveforms, as well as failure modes and effects. The procedural interface specifies how signals are exchanged. RS-485 is another serial data transmission method. This standard defines a method for generating ones and zeroes as voltage pulses. Remember, for all the data handling, framing, packeting, routing and addressing performed by the upper layers, it still comes down to pushing ones and zeroes over some physical media.