Rockwell Automation 1786-series ControlNet Coax Media Planning and Installation Guide - Manual (Page 75)

Publication CNET-IN002B-EN-P - June 2010 75
Glossary
physical link A set of cables and ports that provides a channel of communication between
stations.
protocol A set of conventions governing the format and timing of data between
communication devices.
PVC cable Polyvinyl cholride cable is a common plastic cable insulation. Special additives
are available to make PVC cable flame-retardant to meet Plenum
specifications.
redundancy The duplication of devices for the purpose of enhancing the reliability or
continuity of operations.
reflections The ‘bounce back’ of signals at the end of the cable.
repeater A two-port component that connects coax cable segments together and
amplifies the signal passing from one segment to the other segment. There are
two types of repeaters: amplifying and regenerating. An amplifying repeater
boosts a signal, including noise, and retransmits it down the network. A
regenerating repeater also boosts a signal, but without noise.
ring topology A network where signals are transmitted from one station and replayed
through each subsequent station in the network. Signal can travel in either
direction of the ring so it creates network redundancy; if the ring breaks in one
place the nodes can still communicate.
series Components connected in series are connected along a single path, so the
same current flows through all of the components.
signal The event or electrical quantity that conveys information from one point to
another.
surge-suppression The process of absorbing and clipping voltage transients on an incoming AC
line or control circuit. MOVs (Metal-Oxide Varistors) and specially designed
R-C networks are usually used to accomplish this.
tap A connection to a trunk cable. The tap allows part of the signal on the trunk to
be passed to a station, and the signal transmitted by the station to be passed to
the trunk.
tap dummy load A device that terminates an unused tap.
terminating resistor A 75
Ω
resistor (ControlNet) mounted in a BNC plug to absorb electrical
energy of the signal at the end of the cable to prevent reflections. Ethernet
uses a 50
Ω
resistor. There also are TNC terminating resistors.
topology The way a network is physically structured.
USB A Universal Serial Bus (USB) establishes communication between device and a
host controller.