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LonWorks

The Echelon Corporation through its LonWorks technology has provided a platform for developing open control systems offering distributed, network intelligence.

A LonWorks network is usually a peer-to-peer network where each device controls its own actions and shares information with its neighbours as needed to control the entire system.

Normally the nodes will exchange data rather than commands. In this approach, application data items such as temperatures, pressures, states, and other data items can be sent to multiple devices, each of which may have a different application for using that data item. These data items may be considered as global data variables on the network and are in LonWorks technology referred to as Network variables. If a device updates the value of a network variable this new value will automatically be propagated on the network and the other devices may be aware of the new value.

Interoperability is the keyword in the LonWorks technology. It is a condition that ensures that multiple devices (from different manufactures) talk the same language and understand each other on the network.

To achieve interoperability it is not enough to just be on the same network, have the same type of transceiver or be able to send and receive network variables. The nodes must also be able to understand the content of the network variable. For instance the nodes need to know if the temperature is in degrees Fahrenheit or Celsius or if a flow value is in litre/sec or ml/sec. Hence, a condition for interoperability is that the data items are represented in a standardized way. This has been accomplished by the LonMark Association, an independent organization of LonWorks developers, system-integrators, and end-users. Members in the LonMark Association work together to define the standards, ensuring interoperability between LonWorks devices from multiple manufacturers.

In LonWorks technology, interoperability is promoted by the use of Standard Network Variable Types (SNVT). For a SNVT type network variable, the unit, resolution and range are defined. For example, if a SNVT_speed network variable is used every LonWorks interoperable node knows that the unit is m/s, the resolution is 0.1 m/s and the range is 0 to 6553.5 m/s. Today there are more than 140 different SNVT:s.

The most prevalent transceiver is the FTT-10A free topology transceiver. It communicates at a data rate of 78 kbit/s over a twisted pair cable in any topology including star, bus ring or combinations. The convenience of the free topology makes it desirable for the interconnection of sensors and controllers in today´s control network. The added benefit is a non-polarized interface eliminates one of the biggest problems in installation today reversing the communications wires.

Offering the same flexibility in topology, the LPT-10 link power transceiver can be powered from the same pair as it communicates on.
There are also a 1 250 kbit/s twisted pair bus transceiver as well as the PLT-22 power line transceiver which has advanced signal processing, error correction and an unique dual carrier frequency feature making it possible to communicate very effectively in the presence of electric noise, appliance motor noise, dimmers, PCs and televisions.

The PLT-22 transceiver can be configured for operation in the CENELEC A-band for European utility applications or for the CENELEC C-band for consumer applications.

There are also transceivers for fibre optic cable, radio and infrared available.

One feature of LonWorks technology is the customer's freedom to use multiple communication media in a control network. Echelon's routers seamlessly move LonWorks data from one medium to another.

Routers interface between a high-speed backbone media and a slower media provides both logical and physical network segmentation and protection.

During quarter 1 year 2001, Capelon and Westermo will release a range of products that could be used to create a fiber optic link between two or more LonWorks network.

The products range from simple 78 kbit/s point-point physical layer repeaters/converters to intelligent 1.25 Mbit/s redundant ring topology routers. Fiber optics provides advantages like immunity to electrical interference, reliability and long-distance communication.

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	LonWorks
	The Echelon Corporation through its LonWorks technology has provided a platform for developing open control systems offering distributed, network intelligence. A LonWorks network is usually a peer-to-peer network where each device controls its own actions and shares information with its neighbours as needed to control the entire system. Normally the nodes will exchange data rather than commands. In this approach, application data items such as temperatures, pressures, states, and other data items can be sent to multiple devices, each of which may have a different application for using that data item. These data items may be considered as global data variables on the network and are in LonWorks technology referred to as Network variables. If a device updates the value of a network variable this new value will automatically be propagated on the network and the other devices may be aware of the new value. Interoperability is the keyword in the LonWorks technology. It is a condition that ensures that multiple devices (from different manufactures) talk the same language and understand each other on the network. To achieve interoperability it is not enough to just be on the same network, have the same type of transceiver or be able to send and receive network variables. The nodes must also be able to understand the content of the network variable. For instance the nodes need to know if the temperature is in degrees Fahrenheit or Celsius or if a flow value is in litre/sec or ml/sec. Hence, a condition for interoperability is that the data items are represented in a standardized way. This has been accomplished by the LonMark Association, an independent organization of LonWorks developers, system-integrators, and end-users. Members in the LonMark Association work together to define the standards, ensuring interoperability between LonWorks devices from multiple manufacturers. In LonWorks technology, interoperability is promoted by the use of Standard Network Variable Types (SNVT). For a SNVT type network variable, the unit, resolution and range are defined. For example, if a SNVT_speed network variable is used every LonWorks interoperable node knows that the unit is m/s, the resolution is 0.1 m/s and the range is 0 to 6553.5 m/s. Today there are more than 140 different SNVT:s. The most prevalent transceiver is the FTT-10A free topology transceiver. It communicates at a data rate of 78 kbit/s over a twisted pair cable in any topology including star, bus ring or combinations. The convenience of the free topology makes it desirable for the interconnection of sensors and controllers in today´s control network. The added benefit is a non-polarized interface eliminates one of the biggest problems in installation today reversing the communications wires. Offering the same flexibility in topology, the LPT-10 link power transceiver can be powered from the same pair as it communicates on. There are also a 1 250 kbit/s twisted pair bus transceiver as well as the PLT-22 power line transceiver which has advanced signal processing, error correction and an unique dual carrier frequency feature making it possible to communicate very effectively in the presence of electric noise, appliance motor noise, dimmers, PCs and televisions. The PLT-22 transceiver can be configured for operation in the CENELEC A-band for European utility applications or for the CENELEC C-band for consumer applications. There are also transceivers for fibre optic cable, radio and infrared available. One feature of LonWorks technology is the customer's freedom to use multiple communication media in a control network. Echelon's routers seamlessly move LonWorks data from one medium to another. Routers interface between a high-speed backbone media and a slower media provides both logical and physical network segmentation and protection. During quarter 1 year 2001, Capelon and Westermo will release a range of products that could be used to create a fiber optic link between two or more LonWorks network. The products range from simple 78 kbit/s point-point physical layer repeaters/converters to intelligent 1.25 Mbit/s redundant ring topology routers. Fiber optics provides advantages like immunity to electrical interference, reliability and long-distance communication.
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