Symmetricom 1100 User Manual

Chapter 1 Overview of the TimeProvider
Synchronization Status Messages (SSMs)

 TimeProvider User’s Guide

The TimeProvider handles SSMs in accordance with T1X1.3 TR33, T1.101-1999, 
GR-253, and GR-378. 

Input SSMs
The TimeProvider extracts and decodes the SSM (if present) on the available 
inputs. Using this information, the TimeProvider can automatically select the input 
with the higher quality level.

You can manually provision the input quality level for those signals that do not have 
SSM information or you can provision INP1 and INP2 to read the SSM on the input; 
in either case the quality level of the reference input becomes the system’s quality 
level, which is passed through to the outputs in the output SSM. If the IOC enters 
the Free-run or Holdover mode, the system’s quality level is determined by the 
CLKTYPE parameter for the local oscillator on the selected IOC module. You can 
provision the CLKTYPE parameter to Type I, Type II, ST2, or ST3E.

Output SSMs
You must provision the TimeProvider’s outputs according to the type of SSM 
operation you are using:

For ANSI SSM operation, set the output type to Extended SuperFrame (ESF) for 
ANSI SSM operation.

For ITU SSM operation, set the output type to Channel Associated Signaling 
(CAS) or Common Channel Signaling (CCS) with CRC4 framing. The SSM bit 
location can be set by the user.

SONET Minimum Clock traceable 
(20 ppm clock)

7

SMC

Stratum 4 traceable (32 ppm clock)

8

ST4

Do Not Use for synchronization

9

DUS

Synchronized – Traceability Unknown

0

UNK

Primary Reference Clock

2

PRC

Transit Node

4

SSUT

Local Node

8

SSUL

Synchronization Equipment Clock

11

SEC

Do Not Use for synchronization

15

DNU