VoIP in Industrial Networks

For many years, serial interfaces such as current loop, RS-232, and RS-485 have been the preferred methods for industrial communications. Ethernet offers high reliability with the proven ability to adapt to changing environments, especially new types of media (coaxial cable and wireless transmission, for example). As Ethernet becomes the common interface for interconnection, it becomes natural to use this resource for all communications requirements. Adding voice communications capabilities, by either extending a telephone or offering a hot-line/party-line facility, can be as easy as plugging in a box and a handset. While serial device networks offered a measured level of efficiency, their implementation was very inefficient. Often these networks were made up of many smaller networks. Strings of similar equipment on single-network segments were laid on top of each other over the shop floor. Interestingly enough, this ad hoc architecture did provide a level of protection for the data on each network string. A new piece of gear on one network didn't affect any other network. If expansion was required, an element could be added without much trouble. If needed, a new string could be created. This practice made strings of equipment deterministic in their behavior at the expense of high operational and infrastructural overhead.