Figure 83. Crg Functional View - Alcatel 1850 TSS-320 Technical Handbook

The selectors SEL_A and SEL_B controlling the synchronization sources for the equipment internal clock
(T0) and for the generated output reference clock (T4/T5) are controlled by processes fully independent.
In any operation mode (i.e. locked, holdover and free-running) the stand-by CRG, for instance CRG B,
is phase locked to same synchronization source selected by the active one (CRG A in the example); both
CRG receive the same reference sources and in particular in non locked condition, the stand-by CRG is
synchronized with the local oscillator of the working copy.
To guarantee the hitless switching between the two CRG on manual command, not only the clock but also
the sync pulse generator of the slave copy (CRG B in the example) is kept aligned with sync pulse
generator of CRG copy A acting as master.
The CRG behavior is according to the diagram depicted in Figure 83. on page 134.
T1 T1
T2 T2
T3/6 T3/6
3.7.1.1 Synchronization sources
The T0 clock selector SEL_B selects one reference synchronization source from a number of signals
derived from SDH/PDH signals and/or from external reference (station) synchronization signals:
[1] For SDH network 2 external 2Mhz (T3) or 2Mbit/s (T6) input clocks from POW320 modules (one from
copy A and one from copy B) are supported.
[2] Up to 6 recovered clock from traffic interfaces (T1 and/or T2).
Each optical or electrical interface of any SDH and PDH port card can be provisioned to gain access
to a 6 wires clock bus.
• T1: STM-N transport signals carry (in addition to the payload) reference timing information and
the indication of the quality level of the source generating this timing information, via S1 byte
as defined in Rec ITU-T G.707
Alcatel 1850 TSS-320 Rel. 1.1
134/270 8DG 07734 AAAA Edition 01
Squelch A Squelch A
Sel_A Sel_A
SETG SETG
SEL_B SEL_B
OSC OSC
To companion CRU To companion CRU
From companion CRU From companion CRU

Figure 83. CRG functional view

Sel_C Sel_C
Squelch Squelch
B B
Synchronization Status Synchronization Status
Technical Handbook Common
Functional Description
T4/5 T4/5
T0 T0