Figure 13: Vf Transmission Level Settings - GE JungleMUX 86445-31 Technical Practice And Installation Manual

The Transmission Level Points (TLP) are typically set 5dB above the signal level
that is transmitted in.
frequencies. The signal can exceed the TLP by up to 3.17dBm for µ-law and
3.14dBm for A-law without distortion of the signal.
Since most phones transmit at or around -9dBm, the transmit-in TLP should be
set around -4dBm or greater (typically 0dBm).
The receive-out TLP for the 86445-3X 2W FXS unit is nominally set at -2dBm (if
line impedance is 600 ohms) but should be set for the best voice quality for the
phone set being used.
FXS FXS
Tip Tip
4W / 2W 4W / 2W
HYBRID HYBRID
Ring Ring

Figure 13: VF Transmission Level Settings

NOTE 1: The term dB is a ratio of power where positive dB is gain and negative
dB is loss, whereas dBm is a measure of absolute power in decibels relative to
1mW where 0dBm is 1 mW.
NOTE 2: The term dBm0 is used to express the difference in power between a
signal at any point in a voice network and a reference Transmission Level Point
(TLP) chosen as zero reference level for that point in the network. The dBm0
value of a signal with an absolute power of -10dBm, at a TLP of -5dBm, would be
-5dBm0, 5dB below the reference level. That same signal with an absolute
power of -10dBm, at a TLP of -15dBm, would have a value of +5dBm0, 5dB
greater than the reference level. To calculate the dBm0 value use the following:
Using this formula for the two examples above:
Copyright  GE Multilin Inc. 2002
This is to reduce the quantization error for VF voice
0 dBm0 0 dBm0
point point
D D
A A
I I
N N
TX TX
G G
A A
I I
L L
T T
O O
RX RX
A A
G G
L L
Absolute Power (dBm) – TLP = dBm0
342-86400-445PS
Issue 4.0
October 2006
Page 84
FXO FXO
0 dBm0 0 dBm0
point point
D D
Tip Tip
A A
I I
N N
RX RX
G G
4W / 2W 4W / 2W
A A
I I
L L
HYBRID HYBRID
T T
Ring Ring
O O
TX TX
A A
G G
L L
-10 – (-5) = -5 dBm0
-10 – (-15) = +5 dBm0
P P
A A
B B
X X