Pendulum GPS-12, Руководство пользователя

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Reference Oscillators
The GPS-12 is equipped with an oven-con-
trolled crystal oscillator (OCXO), the GPS-12R
has a standard rubidium oscillator, and the
GPS-12R/HS has a high-stability, low phase
noise rubidium oscillator. The GPS-12RG is
also equipped with the latter oscillator.
Two Operating Modes
The disciplined mode is the default mode. It
eliminates long-term frequency drift, also
called aging. As long as there is a valid satellite
signal, the local rubidium oscillator is continu-
ously adjusted to minimize the deviation from
the satellite-derived reference signal.
The hold-over mode is entered either automati-
cally, if the satellite contact is lost, or manually.
The automatic adjustment is replaced by the
normal aging characteristics of the rubidium
oscillator.
The manual hold-over mode is mainly intended
for the hopefully rare occasions when the satel-
lite contact is sporadic, causing unacceptable
mode switching interference.
Portability
By means of Option 78 or Option 78/HS, an in-
ternal rechargeable battery unit, it is possible to
maintain stability during transportation, as the
internal reference oscillator is continuously
powered.
Field use without access to AC line power is
also practicable.
Option 78/HS has the additional feature of ac-
cepting an external 12 V
DC
supply. Thus it is
possible to realize a true uninterruptible power
supply (UPS), as the DC source and the AC
source can be applied simultaneously. The AC
source takes precedence, as long as it is present,
and so does the external DC supply over the in-
ternal battery, which is kept charged by one of
the external sources.
In case of a power line failure you will benefit
from double security, if you utilize an external
DC source in addition to the AC supply.
Stationary Use
Option 77 makes it possible to apply -48 V
DC
as an alternative to the standard AC line volt-
age, thus allowing permanent use as local fre-
quency standard in telephone exchange sta-
tions. AC line voltage and -48 V
DC
can be ap-
plied at the same time in order to realize a true
uninterruptible power supply (UPS).
Overall Accuracy
The cesium standards of the satellites are con-
trolled by primary frequency standards like the
US Naval Observatory, and ultimately to all na-
tional standards (e.g. NIST, NPL, PTB, SP
etc.).
1-3
Preface