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APPENDIX D
DEALER DESKS
BRIDGING
(CONFERENCING)
CIRCUITS
D-12
may need to select the +7 dBm output level from the CELP and attenuate
the VF signal appropriately.
Steps for the alignment of 4-WIRE CIRCUITS
1. Identify the test point for alignment from the Loss Plan. If a loss plan
is not already in place, it is necessary to compile one prior to
alignment. During the alignment process any errors in the documen-
tation should be corrected for future reference.
2. Set up a tone generator to send a tone at 0 dB (–16 dBm with –16 TLP).
Use the meter to assure that the VF signal level being transmitted is
correct (This requires setting the meter to terminate, so be sure that
the meter is reset to the 'bridge' setting upon completion of the mea-
surement). Disconnect the terminal equipment (caution should be
used not to double terminate the equipment as tone generators have
600 ohm termination). Attach the tone generator into the channel
module.
3. Using the meter, measure the tone at all points along the circuit
aligning the VF signal to Loss Plan specifications.
should proceed such that the first point tested is the closest to the source
of the tone working toward the furthest test point from the tone. This is
necessary as all adjustments which are being made during the
procedure will effect the levels at points further down the circuit.
4. Now perform the same procedure with the tone originating at the oppo-
site end of the circuit.
In the case of Dealer Desks, independent adjustments are made for the
phone and microphone/hoot 'n holler circuits. The same rules apply to
both regarding VF signal levels and Echo Return Loss.
The Bridge circuits are the key element in Conference Networks. They
should be adjusted first. Accuracy is very important since this type of ap-
plication is most demanding in terms of voice levels (and hence voice
quality through the CELP).
When adjusting the Bridge circuits levels, ensure that where possible the
actual loads are used at each port. Do not use dummy loads since dummy
loads may differ slightly in the resistive or reactive components of
impedance, with consequent effects on VF signal levels. Ensure that there
are no VF signals on unused ports when making these measurements.
VF Signal levels in any direction through the Bridge circuits should be
balanced to within 0.1 dB in any direction. Tones should be used univer-
sally for these adjustments and meters should be used to monitor signal
levels in Bridged (High Impedance) mode.
When the Bridge circuits are each independently balanced, the phones to
and from the Bridge circuits can have their levels adjusted. Finally the
links between Bridge circuits can have their levels adjusted. When you
tandem any digital voice links, CELP included, you can expect a certain
amount of degradation in signal quality as you increase the number of
tandemed links.
You should ensure that no acoustical feedback paths exist. This is espe-
cially true where dealer desks are used (hoot 'n holler/telephone
This
alignment
ar-
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