Specifications
G
STRUCTURED
CABLING
TM
www.signamax.eu
G6
Length
There is a direct proportionality between the length and attenuation (i.e. the longer the length of cable, the higher the
attenuation). Testing devices use so-called TDR (Time Domain Reflectometery) for measuring lengths. This means that
a pulse is sent down the cable, then it is reflected back onto the remote unit, and subsequently the time during which
the pulse travels the whole track is recorded. Based on the NVP (i.e. Nominal Velocity of Propagation, which expresses
the signal speed in the cable as compared to the speed of light in a vacuum), the length of the measured segment is
calculated. This concerns the length of the twisted pairs inside the cable (so-called electrical length), not “untangled”
cable (so-called physical length). At 85 m, the variation between electrical and physical length can be up to 5 m
depending on the twisting of each pair.
Return Loss
Return Loss shows the reflection of the signal because of varying impedance at different cable parts. Due to these
impedance imbalances, part of the energy can return to the transmitter, which can cause the signal interference.
When testing structured cabling, two basic topologies are used:
Permanent link—the connection from the patch panel to the work area telecommunication outlet (i.e. horizontal
cabling); this is the most permanent fixture on the structured caballing and cannot easily be taken apart. The maximum
permitted length is 90 m.
Channel—the connection from the active device (e.g. switch) in the data rack to the network card in the computer,
patch cords included. The recommended maximum length of an equipment cord in the data rack is 5 m; the maximum
recommended length for work area cord is 20 m. The length of the channel (i.e. the horizontal caballing plus equipment
cord as well as work area cord) should not exceed 100 m.
Work Area
Cord
Equipment
Cord
max. 100 m
Horizontal Cabling
max. 90 m
Outlet
Outlet
Structured Cabling Testing
Horizontal Cabling
Patch Panel
Patch Panel