Operation Manual

Chapter 6
Structured cabling testing
64
6.11. Insertion Loss Test (Attenuation)
This test determines the overall insertion loss of the signal in the cable and checks
compliance with limits. A minor loss is the prerequisite for a faultless transmission. Insertion
loss measurement is performed by feeding a signal with known amplitude into the Remote
handset (RH) and then reading the amplitude on the Display handset (DH).
Illustration 6.11. Loss Test
6.11.1. Insertion Loss test Error
The insertion loss reduces the signal in the cable. Loss increases with cable length, signal
frequency and temperature. With the aid of loss tests it is possible to detect faults in cable,
connections and connection technology. A high loss value in dB indicates a strong loss, and
thus a higher signal reduction.
6.12. Return Loss Test
This test determines the relation between reflected and transmitted signal amplitude. High-
grade cable lines exhibit only minor reflection, thus demonstrating a good impedance
adjustment of the individual components connected to the cable.
Illustration 6.12. Return Loss Test
6.12.1. Return Loss Test Error
Same as with loss, an excessive return loss also results in signal reduction at the reception
end. It also indicates that an impedance mismatch exists in a section of the cable. A value of
20 dB or higher indicates a good twisted-pair cable.