Installation guide

Glossary
890 USE 101 00 October 2006 155
tap A passive device used to isolate a node from the trunk cable. It allows only a portion
of the signal to be transmitted through a port on the tap.
tap insertion loss The amount of signal loss in the trunk caused by inserting a tap.
TDR (time
domain
reflectometer)
A test device for measuring the integrity of a medium regarding impedance
mismatch and connections.
terminator A piece of hardware containing a 75 Ω resistor, used at the ends of the trunk cable,
at each node, and at each tap outlet to match the characteristic impedance of the
cable. See also characteristic impedance.
through loss The signal loss through a device caused by physical insertion of the device in the
trunk cable. See also insertion loss.
topology The complete media specification. The topology should be mapped into a log with
all installation details for future reference.
transfer
impedance
A measure of cable’s ability to reject noise. The lower the number, the better the
cable.
trunk cable The main cable running from the RIO processor upon which taps are installed,
permitting the drop adapters to connect to the cable system.
trunk terminator A precision terminator used at the two ends of the trunk cable. See also terminator.
velocity of
propagation
The speed of the signal in the cable, expressed as a percentage of the speed of light
in free space.
VSWR (voltage
standing wave
ratio)
The measure of the signal reflected back from a transmitted signal. Lower ratios
indicate better impedance match and cause less signal to be reflected back at the
transmitting source.
T
V
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com