The Highway Addressable Remote Transducer (HART) protocol was originally developed and is currently managed by the HART Communication Foundation (HCF). Based upon Bell 202 modem technology, it first allowed digital configuration of "smart" 4-20 mA industrial field devices.

Originally developed by Siemens, PROFINET is the Ethernet-based fieldbus protocol which integrates well with the earlier PROFIBUS-DP protocol. PROFINET is maintained by PROFIBUS and PROFINET International (PI) which is based in Germany.

PROFINET is currently the most popular Ethernet fieldbus in Europe. It is primarily utilized by Siemens, but PROFINET controllers and devices are available from several manufacturers.

PROFIBUS-PA is an intrinsically-safe version of PROFIBUS-DP used in the process automation industry. Like PROFINET and PROFIBUS-DP, PROFIBUS-PA is managed by PROFIBUS and PROFINET International (PI), based in Germany.

One of the world's most successful fieldbuses, PROFIBUS-DP is a serial bus protocol, which allows several devices to be connected on a single pair of wires. The PROFIBUS-DP protocol was designed by Siemens for distributed industrial I/O. Like PROFINET and PROFIBUS-PA, PROFIBUS-DP is managed by PROFIBUS and PROFINET International (PI), based in Germany.

The EtherNet/IP protocol is the Ethernet-based manifestation of ODVA's Common Industrial Protocols fieldbus suite. It is one of the most popular industrial fieldbuses in the United States.

EtherNet/IP utilizes standard Ethernet and Internet protocols, allowing for a wide range of choices for cabling media and network equipment, as well as for simple integration of EtherNet/IP with company enterprise networks. EtherNet/IP can be used as a high speed factory network backbone, or directly with intelligent devices. Because it implements CIP, it interoperates seamlessly with other CIP based protocols such as DeviceNet.

DeviceNet protocol is the device-level, CAN-based manifestation of ODVA's Common Industrial Protocols (CIP) fieldbus suite. It is one of the most popular fieldbuses in the world today. Over 700 vendors support the DeviceNet standard worldwide.

DeviceNet utilizes the inherently robust CAN data and physical layers for data communication. In addition, DeviceNet takes advantage of the CAN power connection to supply operating voltage to devices with limited power requirements. The multi-drop bus structure of CAN simplifies wiring and minimizes cabling costs, as well as improving reliability by reducing the number of required connection points.

The Controller Area Network was originally developed by the Robert Bosch Corporation as a robust, low-speed messaging protocol for automotive use. The CAN protocol is now maintained by the ISO standards organization.

The Controller Area Network was originally developed by the Robert Bosch Corporation as a robust, low-speed messaging protocol for automotive use. The CAN protocol is now maintained by the ISO standards organization.

CANopen is an open protocol developed by the CAN in Automation (CiA) organization in Nuremburg, Germany. Like many other application protocols, CANopen uses the robust and ubiquitous CAN physical and link layers for data communication.

The CANopen physical layer is specified for a range of transmission speeds between 10 Kbits/second and 1 Mb/second. Because of the nature of the underlying CAN error checking protocol, the maximum cable length for a CANopen network depends upon the bit rate chosen. At the lower speeds, CANopen can be used for controlling all the cars in a passenger train, whereas the higher speeds are primarily reserved for communications within a few meters.

As an open member organization, CiA publishes a collection of standard CANopen device and system profiles for a variety of uses in the transportation, construction, agriculture, industrial automation, and medical device industries. Dozens of manufacturers are members of the CiA and supply hundreds of CANopen products to customers all over the world.

The Distributed Network Protocol was developed by the Harris company to provide interoperability between electric substations, intelligent electronic devices, remote terminals, and master stations in the electric utility industry. Since introduction, it has been expanded to include other industries, such as water/wastewater, oil and gas, and transportation. The open protocol is currently managed by the DNP Users Group. Hundreds of vendors across the world supply equipment which conforms to DNP.

The Modbus serial protocol was one of the first industrial communication protocols ever developed. Developed by MODICON, the company that created the PLC, the protocol is a model of simplicity. As a result, it is used all over the world for industrial communications. Because it can be used over modems, it is the de facto communications standard for SCADA systems and remote terminal units (RTU).

The original Modbus ASCII protocol has largely been supplanted by the more versatile RTU protocol. The Modbus/RTU messaging structure is consistent with the message structure for Modbus/TCP, allowing for seamless operation between the two protocols. The Modbus Organization has even published specifications on how a gateway between the two protocols should operate.

Modbus/TCP is the Ethernet manifestation of the venerable Modbus protocol. Modbus/TCP utilizes standard Ethernet and Internet protocols, allowing for a wide range of choices for cabling media and network equipment, as well as for simple integration of Modbus/TCP with company enterprise networks. Modbus/TCP can be used as a high speed factory network backbone, or directly with intelligent devices.

Modbus+ (pronounced, "Modbus Plus") is a proprietary, multi-drop peer-to-peer bus protocol using a token-passing scheme for data transmission at a higher data rate than Modbus serial protocols. Schneider Electric maintains control of the Modbus+ protocol.

Foundation Fieldbus (FF) is primarily used in the process control industry. It was developed and is maintained by the Fieldbus Foundation. It was originally intended to be the digital replacement for the ubiquitous 4-20 mA standard that still commands 85% of the field device market share.

Foundation Fieldbus operates on two physical layers. Fieldbus H1 uses an RS-485 physical layer operating at 31.25 kbit/second over standard twisted pair cabling H1 is recommended for the field device level. Fieldbus HSE (High Speed Ethernet) runs over standard Ethernet, and recommended for backbone communications in a plant.

The Actuator Sensor interface was originally developed by Siemens to provide a low-cost, efficient wiring & communication system for low-level industrial field devices. The protocol is currently owned & managed by the AS-Interface organization.

LonWorks was developed by the Echelon Corporation and is maintained by a variety of standards bodies, including ANSI. It offers an integrated solution to a variety of control system applications. Once a closed, proprietary system, Echelon Corporation "opened" the protocol in the 1990s to allow for greater adoption of the technology.