Jackson Labs RSR GNSS Transcoder, Руководство пользователя

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RSR GNSS Transcoder™ User Manual
4.7.1 SYNChronization:HOLDover:DURation?
This query returns the duration of the present or most recent period of operation in the holdover. This
is the length of time the reference oscillator was not locked to the external GNSS receiver 1PPS, and
is thus “coasting”. The first number in the response is the holdover duration. The duration units are
seconds, and the resolution is 1 second. If the Receiver is in holdover, the response quantifies the
current holdover duration. If the Receiver is not in holdover, the response quantifies the length of the
previous holdover. The second number in the response identifies the holdover state. A value of 0
indicates the Receiver is not in holdover; a value of 1 indicates the Receiver is in holdover.
4.7.2 SYNChronization:HOLDover:INITiate
The SYNC:HOLD:INIT and SYNC:HOLD:REC:INIT commands allow the user to manually enter
and exit the holdover state, even while GNSS signals are still being properly received. This
forced-holdover allows the unit to effectively disable GNSS disciplining of the internal oscillator,
while still keeping track of the state of the 1PPS output in relation to the UTC 1PPS signal as
generated by the GNSS receiver. When the unit is placed into forced-holdover with this command,
the unit will indicate the time interval difference between the 1PPS output and the GNSS receiver
1PPS by using the SYNC:TINT? command up to a limit of +/-2000ns. This allows the user to see the
oscillator drift when not locked to GNSS signals for testing purposes, or to prevent the GNSS
receiver from being spoofed and affecting the oscillator frequency accuracy. All other
frequency-disciplining functions of the unit will behave as if the GNSS antenna was disconnected
from the unit while in this forced-holdover state.
4.7.3 SYNChronization:HOLDover:RECovery:INITiate
This command will disable the forced holdover state (see the SYNC:HOLD:INIT command). The
unit will resume normal GNSS disciplining operation after this command has been sent.
4.7.4 SYNChronization:SOURce:MODE
This command selects between the EXTernal, GPS, and NMEA sync modes. Both the EXTernal and
GPS modes use the same 1PPS input, but the GPS mode also gates the 1PPS based on the GNSS
status of the external receiver as indicated in the NMEA serial sentences from the GNSS receiver.
The External mode uses only the 1PPS reference input to discipline the oscillator.
The NMEA sync mode uses only the NMEA input to synchronize the system time to
millisecond-level synchronization. The NMEA sync mode is required to transcode without a 1
The format of this command is:
SYNChronization:SOURce:MODE <GPS | EXTernal | NMEA>
4.7.5 SYNChronization:SOURce:STATE?
This command is not implemented in the RSR GNSS Transcoder™.