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Page 166 of 544 Transmission parameters
553-3011-100 Standard 14.00 January 2002
Input impedance and balance impedance
Input Impedance for a port is the impedance as seen looking into the port from
the tip and ring.
The Balance Impedance is the output source impedance of the port and is
designed to match the impedance of the transmission line plus the far end
trunk.
Return Loss
The return loss measures how closely the input impedance matches the
required impedance (source impedance). Return loss at an impedance
discontinuity in a transmission path is the ratio (in dB) of the power level of
an incident signal to the power level of the resulting reflected signal.
Echo Return Loss (ERL) is a weighted average of the return loss value over
the frequency range of 500 to 2500 Hz.
Single Frequency Return Loss (SFRL) is the lowest value of return loss in the
frequency range of 200 to 3200 Hz.
Table 42
Input impedance/balance impedance
Connection System Input Impedance Balance Impedance
500/2500 Line IPE 600 600
2 Wire E&M Trunk IPE 600 600
4 Wire E&M Trunk IPE 600 600
DID/DOD/LOOP TIE
Trunk
IPE 600/900 600/3COM
(3 COM is the EIA
termination of 350 +
1000//0.21 µ F)
C.O.Trunk IPE 600/900 600/3COM
(3 COM is the EIA
termination of 350 +
1000//0.21 µ F)