Gossen MetraWatt U1601, Operating Instructions Manual

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Gossen Metrawatt GmbH 61
11 LON Bus System Structure
The most commonly used transmission medium for industrial and building management
applications is twisted pair copper cable, which is used together with the electrically
isolated FTT-10A transceiver. Both of the conductors can be connected to either pole,
and installation is thus reverse polarity protected.
Maximum transmission distances are influenced by the electrical characteristics of the
cable, and the network topology. Utilized cables should comply with the stipulated
specifications in order to prevent interference during communication. Due to the
possibility of reflections, only one cable type may be used in any given bus segment.
Network Topologies:
If a bus structure is used, the components are connected in parallel, one after the other.
A bus terminating resistor must be used at each end. Branch lines may not exceed a
length of 3 meters. Only one bus terminator is required with free topologies, but
transmission distances are limited in this case.
If repeaters are used, the bus signal can be boosted thus increasing maximum possible
transmission distance. Due to response characteristics, only one passive repeater may
be included in any given bus segment. The transition to other physical transmission
media, and/or targeted forwarding of data packets to individual bus segments, is
accomplished by means of routers.
The following recommendation is based upon experience gained by Gossen Metrawatt
GmbH during installation and start-up of LON systems. The environment within which
the cable is laid has a decisive influence on correct cable selection, and must therefore
be taken into consideration during the planning stage. All generally applicable directives
for laying control and telecommunications cables must be adhered to during installation.
Bus Topology
(bus terminator at both ends)
Free Topology
(bus terminator at one end)