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<div class="div">
<h1>BSC’s Clock And Tone Generator</h1>

<p>The Clock and Tone Generator (CL1TG or CL3TG) generates
the basic timing signals needed in the BSC, either independently or synchronised
to a frame alignment signal provided by the Exchange Terminal (ET). In a single-rack
BSC, the CL1TG distributes the basic timing signals directly to the cartridges
needing them while a BSC composed of two racks contains a special Clock and
Alarm Buffer (CLAB) for the distribution of basic timing signals.</p>


<p>In addition to the basic timing signals, the CL1TG/CL3TG
also generates the tones needed in the BSC. The CL1TG/CL3TG also supervises
the operation of the clock equipment and tone generator and conveys supervision
data to the Operation and Maintenance Unit (OMU). The active CL1TG/CL3TG synchronises
the operation of the back-up unit.</p>


<p>A new unit, CL3TG (standard in BSC3i), can be optionally
equipped to the older BSC variants as well. The CL3TG has improved EMC properties
when compared to CL1TG. Frequency stability in the CL3TG is as in the CL1TG.
In the printed board, signal wirings are covered between the earth layers.
The edges of basic timing signals going out from the unit are made less steep.
Filtering in the incoming direction of the power supply is improved. The ESD
tolerance of the outgoing basic timing circuits is improved.</p>


<p>Usage/equipping: User can connect up to four synchronisation
inputs to the unit. Also two external synchronisation sources can be connected
to the unit. A more detailed description of this PIU can be found in plug-in-unit
description, which is included in the BSC customer documentation (NED).</p>


<p>The requirement for the CL3TG is that CLOC cartridge is
equipped to the BSC. This means that in some old type BSC’s the CLAC cartridges
needs to be replaced with CLOC cartridges before the CL3TG’s can be installed.</p>


<p>CL3TG must not be installed to work in pair with the CL1TG,
except temporarily when the plug-in unit is changed.</p>


<a name="feb26414241522" shape="rect"></a>
<dl class="note-notification">
<dt class="note-caption">Note</dt>
<dd>CL3TG is optional for older BSC variants (BSCE/BSCi/BSC2/BSC2i).</dd>
</dl>


<p>The following table clarifies the differences between the
versions of the CLxTG:</p>


<a name="feb26414253423" shape="rect"></a>
<div>
<p>Table: Differences between the versions of the CLxTG</p>


<table border="1">
<thead>
<tr align="left" char="" charoff="50" valign="bottom">
<th colspan="1" rowspan="1" valign="top"><p></p>


 </th>
<th colspan="1" rowspan="1" valign="top"><p>Synch inputs from ETs</p>
</th>
<th colspan="1" rowspan="1" valign="top"><p>External Synch Inputs (G.703)</p>
</th>
<th colspan="1" rowspan="1" valign="top"><p>Oscillator stability/day</p>
</th>
</tr>
</thead>
<tbody>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>CL1TG</p>
</td>
<td colspan="1" rowspan="1"><p>3</p>
</td>
<td colspan="1" rowspan="1"><p>-</p>
</td>
<td colspan="1" rowspan="1"><p>5E-9</p>
</td>
</tr>
<tr align="left" char="" charoff="50" valign="top">
<td colspan="1" rowspan="1"><p>CL3TG</p>
</td>
<td colspan="1" rowspan="1"><p>4</p>
</td>
<td colspan="1" rowspan="1"><p>2</p>
</td>
<td colspan="1" rowspan="1"><p>5E-9</p>
</td>
</tr>
</tbody>
</table>
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