• The Modbus Organization is a group consisting of independent users and automation device manufacturers who manage the development and use of the Modbus protocols. Their website contains information about the Modbus protocols, as well as technical resources for development, integration and testing of Modbus. It also includes directories of Modbus suppliers and industrial devices utilizing Modbus (http://www.modbus.org/).

• The DNP Users Group is a nonprofit organization that maintains and promotes the Distributed Network Protocol (DNP3). Their website provides documentation on the uses and benefits of DNP3, as well as technical documents and conformance testing. It also includes member directories and listings of all conformance tested products (http://www.dnp.org).

• The OPC Foundation is an organization that maintains the open specifications of the OPC protocol, in an effort to standardize and ensure interoperability of process data communications. Their site includes the latest resources for OPC Classic, OPC UA, and OPC XI (.NET). It provides whitepapers, sample code, technical specifications and software development kits. The website also includes member directories and product lists, as well as technical support, webinars, and other resources (http://www.opcfoundation.org/).

• ODVA is an international association made of automation companies, which manages the development of DeviceNet, EtherNet/IP, CompoNet, and ControlNet protocols utilizing the Common Industrial Protocol (CIP). The ODVA website provides technical specifications, conformance testing policies, training and other resources. It also includes member and product directories (http://www.odva.org).