M e r i d i a n I I U s e r M a n u a l
16
C H A P T E R T W O
17
M e r i d i a n I I U s e r M a n u a l
B A S I C I N S T A L L A T I O N
This last line is the standard Meridian II prompt. After configuring the unit, you should change the
passwords using the Linux
passwd
command issued from the prompt.
Issuing
exit
will close the
ssh
session.
Using HTTPS
You may monitor the status of the Meridian II via the HTTPS interface. For security reasons, you
may not change any settings via the HTTPS interface. See
Chapter 4 - HTTPS
for more information.
IMPORTANT
SSH, Telnet, SNMP and HTTPS are all enabled with default passwords. To ensure security, change the
passwords or disable the protocols.
To change the passwords for SSH, Telnet and HTTPS use the Linux
passwd
command. To change the
passwords/community strings for SNMP see
Chapter 6 - SNMP
.
To disable Telnet, SSH, SNMP and HTTPS see
Chapter 5 - Security, Disable Protocols
.
Connecting Instruments
to the Meridian II
Rear-panel mounted BNC ports provide the means of connecting your equipment to the Meridian II.
The standard Meridian II provides two precision output signals capable of driving properly termi-
nated coaxial cables: 1 PPS and AM Code. These two signals are DC-coupled and sourced from
Advanced CMOS (ACMOS) drivers which are able to maintain output TTL levels into a 50-ohm
load. The optional low-phase noise, spectrally pure sine wave outputs are capable of driving 1 Vrms
into a 50-ohm load. If your unit is equipped with other optional timing or frequency outputs, these
will also be designed to drive a 50-ohm load. Care should be taken not to short circuit these outputs
or to connect them to other voltage sources.
If your unit is equipped with the optional Alarm Output, it will be available on a rear-panel BNC jack
labeled “ALARM”. Care should be taken not to directly connect this open-collector output to a volt-
age source. A series current-limiting resistor of at least 1k ohms in value should be used. The pull-up
voltage must not exceed 40V.
If your primary application for the Meridian II is as a frequency standard and you have not purchased
one of the optional higher-stability oscillators, you should consider operating with the display set to
view the Receiver State. (See
Chapter 12 - Front-Panel Keypad and Display
.) With this display in
view you will always know whether the Meridian II is currently locked to a GPS signal while you are
performing measurements based on its frequency outputs. The holdover frequency accuracy of the
standard TCXO will degrade to the 5x10
-8
level fairly quickly following GPS signal loss, depending
upon the ambient temperature.
Summary of Contents for Meridian II
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