Figure 84. Output Timing Reference Configuration - Alcatel 1850 TSS-320 Technical Handbook

• T2: 2 Mbit/s transport signals may carry (in addition to the payload) reference timing information
and the indication of the quality level of the source generating this timing information, via the
San bits as defined in Rec ITU-T G.704
Note -T2 may also indicate those PDH signals 125ms framed like 34Mb/s and 140Mb/s
specified in ITU-T G.832 carrying (in addition to the payload) sync information;
[3] Local and remote oscillators (OSC) clocks.
The local oscillator clock is connected to the local (active) SETG and to the remote
3.7.1.2 Output clock generation
One redundant external station output reference clock is provided by each PSF card; these signals can
be set either as 2Mhz without SSM information (T4) or 2Mbit/s with SSM information (T5) output
references.
The T4/T5 clock selector (SEL_A) will receive the same references defined for T0 generation with the
exception of the remote T0 clock; this distribution is in line with ITU-T G.781
Note -ITU-T G.781 allows the use of the station clock input as a source for the station clock output, either
directly or via SETG block according to SEL_A and SEL_C configuration. This functionality is intended
just for timing quality monitoring purposes and not as normal operation mode.
There is not any restriction about the number of signals taken from each board. The only constraint is that
the six T1/T2 timing sources are shared between T0 and T4/T5 selection processes: so the 2 selections
for T0 and T4/T5, even if fully independent, have to be done inside the same group of six T1/T2 signals.
The system architecture provide the output clocks in accordance with the so called Protected mode as
indicated in Figure 84. on page 135.
3.7.1.2.1 Output clock squelching
Purpose of the "squelch" function after SEL_A is the qualification process for the timing output; the output
is silenced (fix output level for T4 or AIS activation for T5) to prevent transmission of a timing signal failed
or having a quality (SSM) worse than a provisioned threshold. This is useful for instance in ADM with SSU
configuration.
Technical Handbook Common
Functional Description
One redundant output clock derived One redundant output clock derived One redundant output clock derived
from one STM -N or PDH ifs from one STM -N or PDH ifs from one STM -N or PDH ifs
Port #m Port #m Port #m Port #m SCCRU_A SCCRU_A SCCRU_A SCCRU_A
SCCRU_B SCCRU_B SCCRU_B SCCRU_B
Protected mode Protected mode

Figure 84. Output timing reference configuration

PSF_A PSF_A PSF_A PSF_A
T4/T5 Station clk T4/T5 Station clk T4/T5 Station clk T4/T5 Station clk
Output (copy A) Output (copy A) Output (copy A) Output (copy A)
T4/T5 Station clk T4/T5 Station clk T4/T5 Station clk T4/T5 Station clk
Output (copy B) Output (copy B) Output (copy B) Output (copy B)
PSF_B PSF_B PSF_B PSF_B
Alcatel 1850 TSS-320 Rel. 1.1
8DG 07734 AAAA Edition 01 135/270