With the LonWorks-based communication protocol complete networks made up of interoperable products can be created. The protocol conforms to ISO/IEC 14908 (worldwide), EN 14908 (Europe), ANSI/CEA-709/852 (U.S.) and is also standardized in China. See https://www.lonmark.org.

LonWorks is suited for use with different types of transmission media, such as twisted pair cables, power line, RF, fiber optics or IP (TCP/IP and UDP/IP) It supports straightforward installation with different cabling topologies (e.g., star or line). The connection of objects via bindings (e.g., standard network variables (SNVTs), standard configuration properties (SCPTs)) can be defined at the project engineering stage or can be adapted in the field.


The following figure shows the structure of a Lon network in the FLN



Repeater, e.g., LonWorks physical repeater


Bridge, e.g., L-Switch (Loytec)


Router, e.g., LonWoks router


Gateway, e.g., PXC..., RXZ03.1

See LonWorks networks Checklist (CA110335).


A trunk holds all devices that can communicate with each other directly or via repeater, bridge or router. The term trunk is specific to the Desigo system. One trunk corresponds to one LonWorks project. Trunks can be connected via gateways.


A trunk can be divided into segments. The segments are connected by a router. If there are no routers, the trunk comprises only one segment.

Physical segment

The physical segment is the communication medium. LonWorks devices are connected to the physical segment. One segment can be divided by bridges or repeaters into several segments. The number of devices per physical segment is limited.

System devices


The gateway links trunks. It operates on the application layer of the ISO/OSI layer model. The following LonWorks gateways are available:

The RXZ03.1 point coupler provides a fixed number and type of LonTalk network variables (NV). Each side of the point coupler belongs to a trunk or LonWorks project. The point coupler can be used to implement time-critical connections between two trunks. The point coupler integrates third-party devices that have been engineered with a different tool.

Loytec L-Proxy and Sysmic XFM-LL are freely programmable point couplers. The XFM-LL device may be used, when depicted like a standard third-party device (configuration via its own tool).

The PXX-L.. extension modules let you connect LonWorks devices to the PXC..D modular series.


The LonWorks router operates on the network layer of the LonWorks protocol. It filters data packets based on their subnet ID or group ID. Subnets or groups must never be defined across a router, that is, the subnet IDs and group IDs at each end of the router must never be the same. Routers are used where there is heavy local network traffic. They allow the unloading of unaffected devices from the network traffic. In Desigo there are no large LonWorks networks, as the FLN is divided into trunks. Routers are only required in exception cases.

L-Switch (Loytec)

The L-Switch filters the package on the basis of the subnet/node ID or group ID. It automatically learns the topology and forwards the data packets accordingly. The L-switch does not have to be configured. Unlike the router, there is no need to take account of any addressing limits (allocation of Subnet ID or Group ID).

Physical repeater

LonWorks has physical and logical repeaters. The physical LonWorks repeater does not filter the data packets. It regenerates the electrical signal. One physical LonWorks repeater can be used in the path between any two devices within a segment.

In logical repeaters, the data packet is processed by the neuron chip. This enables several logical repeaters to be connected in series. The disadvantage is that the logical repeater must be configured, and that owing to the limited size of the buffer, it cannot be used for large data packets, that is, for BACnet/LonTalk.