12713140-002-2 Revision E – October 2006 SSU-2000e User’s Guide 175
Chapter 7 Input Module Reference Data
1-Port and 3-Port DS1 Input Modules
Three-Sigma Test
The Input module uses a three-sigma test as part of the phase averaging algorithm
in order to avoid the use of erroneous phase readings. In such tests, the standard
deviation sigma of the phase readings is maintained. Any reading which falls more
than three sigma above or below the mean is considered erroneous.
MTIE Calculation
MTIE is a measurement of the relative noisiness of an input signal. The Input module
automatically (without user intervention) calculates MTIE for its inputs in accordance
with the specifications in (ANSI) T1.101 and reported on demand for a 24 hour period.
MTIE data is retrieved on hour boundaries, though the stop time used may be
current time.
Reported time periods include 0.05, 0.1, 1.0, 10.0, 100.0, 1000.0,
10000.0, and 100000.0 seconds
.
MTIE Alarms
The Input module monitors the ongoing MTIE calculations and logs an alarm if the
MTIE calculation for any of several window sizes exceeds user-set masks.
The Input module software maintains two alarm masks, each with thresholds at 10,
100, 1000, 10,000, and 100,000 seconds. MTIE readings which violate either mask
at any point cause an alarm at a user-settable level (Minor, Major, or Critical). Refer
to Changing Factory Defaults, on page 113, for more information on setting alarm
levels.
Although MTIE is continuously calculated against both clocks, MTIE alarms are
logged only if the measurements against the currently selected clock violate one of
the MTIE alarm masks.
TDEV Calculation
The Input module automatically (without user intervention) calculates TDEV (the
measurement of the frequency components in a series of phase readings) for all its
inputs and reports on the past 24 hours of TDEV history. TDEV is retrieved on hour
boundaries, though the stop time used may be current time.
Reported time periods include 0.05, 0.10, 0.30, 0.60, 1.0, 2.0, 3.0, 6.0, 10.0, 30.0,
60.0, 100.0, 300.0, 600.0, 1000.0, 3000.0, 6000.0, and 10,000.0 seconds.
The input card also contains provisions for zeroing the phase readings for one
channel in response to a command from the Communications module. Once the
phase is zeroed, all subsequent phase measurements are expressed in terms of
how much they differ from the reading at the time the phase was zeroed.
Zeroing the phase invalidates all past phase averages, TDEV, and MTIE.
To Next Page
Loading...
Need help?
General
