GlobalTime Electronic GTT-200 User manual

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Tel:[phone]
Fax:[phone]
Web: www.ntpclock.com
Email: contact @ntpclock.com
Add: A2-1, No.399 Dakang Road, Baoshan District, Shanghai,China
Zip c ode: 200 4 4 3

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Catalog
Catalog
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Chapter 1 The basic information and packaging ································································ 3
1.1 Key features ··································································································································· 4
1.2 Packaging
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1.3 Outline
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1.4 The device profile description ····································································································· 6
Chapter 2 Hardware installation and commissioning
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2.1 The device structure
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2.2 O utdoor i nstallation
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2.3 In door installation ·························································································································· 9
Chapter 3 Equipment m aintenance
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3.1 Indicator state
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3.2 The keyboard display ················································································································· 10
3.3 Server c onfiguration d ebugging ······························································································· 11
3.3.1 User l ogin ······························································································································ 12
3.3.2 Change network setting
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3.3.3 NTP c onfiguration
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3.3.4 SNMP s etting ······················································································································· 14
3.3.5 Heartbeat check (optional function) ·················································································· 14
3.3.6 NTP status ···························································································································· 15
3.3.7 GPS status
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3.3.8 System function ··················································································································· 15
3.3.9 Chage the password ··········································································································· 16
3.3.10 Exit ······································································································································· 16
3.4 Time server log in through the network
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3.4 .1 Time zone display function ...................................................................................... 1 7
3.5 Remote dial-up maintenance
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3.6 Time server log in through the web browser
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3.6.1 The log in interface ··············································································································· 1 9
3.6.2 Network settings ·················································································································· 2 0
3.6.3 NTP settings
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3.6.4 SNMP settings ····················································································································· 2 2
3.6.5 Check the status
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3.7 Client c onfiguration
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3.8 Troubleshooting ·························································································································· 2 5
3.8.1 All indicator lights are off when power is on ···································································· 2 5
3.8.2 Receiving no satellite signals for a long t ime ·································································· 2 5
3.8.3 C an not ping the time server
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3.8.4 Instab le satellite signal, and the machine is in hold mode sometimes ························ 2 6
3.8.5 The client can not receive timing service ········································································· 2 6
3.8.6 How to configure the network equipment to receive time service ································ 2 6
Chapter 4 Detailed performance index of the equipment
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Chapter 5 Appendix ·············································································································· 2 8
Chapter 1 The basic product information and packaging
GTT-200 network time server is the p r ofessional network equipment providing high-stab le
time source . GTT-200 network time server receives GPS satellite signals and extract s the
timing information to adjust the server's local time . It distributes standard time via NTP
protocol (Network Time Protocol) . If a PC or server need s time synchronization services, it

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will run a client program to read the NTP protocol, derive time information, and modify the
time of related equipment.
The n etwork time server is widely used in telecommunications, finance, taxation, public
security and other special networks as well common corporate networks to unif y the
network time.
1.1 Key features
Serves as stratum 1 time server, receive signal from GPS s a t e llite, or GPS and
GLONASS dual satellite(optional), or from external serial port. Can be set as slave time
server to synchronize with host time server.
Adopt RFC1119/1305 NTP protocol (Network Time Protocol) to delivery time
Support RFC1769/2030 SNTP protocol (Simple Network Time Protocol)
Different client programs suppo rt, 98/2000/NT/XP, Linux, Unix, FreeBSD and other
operating systems
Two 10/100M BaseT adaptive network port s
Response capability per unit time: >1000 times per second
The GPS receiving system supports position-holding mode which greatly improves the
functionality of the system
OCXO can be built-in to guarantee the accuracy of time-keeping
Support SNMP, with the serial port to enter
6 lamps display the device working status
1.2 Packaging
Please check the shipping package which should contain the following items:
(1) GTT-200 network time server
(2) Power cable
(3) GPS antenna cable
(4) GPS satellite receiving antenna and the mounting support
(5) This user manual
(6) The software CD
(7) The packing list

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1.3 Outline
With the rapid development of modern society, higher demand on the time precision and
frequency is put on the agenda. Nowadays with the development of modern digital
communication networks and the information superhighway construction, the political,
cultural, technological and social information coordination is based on a strict system of time
synchronization, especially in the communications, electricity, financial securities, computer
networks , production line operation, administration and national defense and other fields
urgently need the tim e synchronization equipment .
Global Positioning Satellite (GPS) signals act as the reference source of GTT-200 network
time server. The time reference contained in the GPS satellite signals synchronize s with the
universal time coordinat ed (UTC) . The long-term frequency stability has achieved the10-13
level of magnitude of cesium atomic clock, which is equivalent to be only 1 second slower
during 30 years. To adjust local time with t his reference signal can eliminate the
accumulation of deviation resulted from the low accuracy of local clock time and also can
greatly improve the timing precision of the server.
GTT-200 network time server use the professional GPS timing receiver . It can receive and
lock the satellite signal fast and reliabl y .
NTP protocol (Network Time Protocol) is a common international network timing protocol. Its
principle is to launch a time polling to the server after an interval of time through the client.
A ccording to a certain filtering algorithm it can calculate the time deviation between the
server and the client as well as the propagation delay caused by network transmission . T hen
according to these two parameters to adjust the client's local time and make it consistent
with the server. Compared to other time calibration pro t ocols, NTP protocol can eliminate
the impact caused by network transmission delay, so it can provide high-precision timing
services. Detailed description can be refer red to the latest protocol standards documents
RFC1305 and RFC2030. GTT-200 n etwork time server can be compatible with NTP v2 / v3 /
v4 in various versions.

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1.4 The device profile description
The front panel description:
3 2 1 0
监测 天线
I
0
I
0
Synchronized *
2009 / 01 / 01 08 : 35 : 26
OK
NTP
GPS
ocxo
M / S
POW 1
POW 2
GLOBALTIME
Figure 1-1 The front panel
The front panel:
VFD display, to show the basic status of the device and the current UTC time
The keyboard, to check and modify the system configuration
Two power lights, to indicate the two-way power supply
Four indicator lights, to indicate the service status of GPS and NTP
The back panel :
Two power sockets with fuse . After opening the fuse base, there are a primary and a
reverse fuse with specification of 0.5A on each side to facilitate users ’ r eplacement.
One anten n a plug as well as 50 ohm BNC Socket on the panel.
Two 10/100M adaptive network port s
One serial port for monitoring.

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Chapter 2 Hardware installation and commissioning
2.1 The device structure
Figure 2-1 Device structure
GTT-200 network time server consists of the outdoor part and interior part. The outdoor part
is composed of the GPS satellite receiving antenna, surge arrester and antenna amplifier
(optional). The function is to complete the reception of satellite signals.
The interior part is the master device of GTT-200 network time server to complete the
functions of the satellite signal demodulation, the local clock calibration, achieving NTP
protocol and so on. It provides NTP timing service to other network equipment by 10M
network ports. The following are the detail installation description of the outdoor part and the
interior part.
2.2 O utdoor installation
The outdoor part is composed of the GPS satellite receiving antenna, transmission cables
and antenna amplifier. The installation attentions are as follows:
At first, the antenna installation location needs to be carefully selected, which will
signi f icantly influence function of equipment. The antenna should be installed in high
position, and can not be blocked by , such as the roof, open top, etc. If you want to achieve
better results, you
’
d better keep the elevation angle of 15 degrees from block ing . Please do
not install the antenna inside the room , because GPS satellite signal is very weak and can
not be received indoors. It does not matter if there are trees or plastic rain shelter above the
GPS receiving
antenna
A ntenna amplifier
Light n ing arrester
T
T
T
TH
H
H
H E
E
E
E

W
W
W
W  R
R
R
R E
E
E
E L
L
L
L E
E
E
E  S
S
S
S  S
S
S
S

 A
A
A
A T
T
T
TM
M
M
M

C
C
C
CO
O
O
OM
M
M
M P
P
P
P  A
A
A
A N
N
N
N Y
Y
Y
Y
 A    S   a 

 S  A  S
 P O W  E RGTT-200

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antenna, but other block will influence the signal significantly. In fact, only a book above the
antenna can completely block out the satellite signal.
Second, a ntenna installation should be lower than the lightning rod or other constructions
that can attract thunderstroke and the installation location should better be 10-15 meters
away from them. GPS antenna itself is rarely struck by thunder blot but is often damaged by
the stong induced electric field resulted from the stuck buildings (the lightning rod, tower, etc)
around. In this circumstance, we should install the arrester in the cable. Normally the
arrester will be installed at the position where the cable goes through the wall. By this, the
arrester can be well earthed. The arrester should also be installed between the feeder and
the equipment. Then lead the grounding wire from the arrester and connect it to the earth.
The earth resistance should be under 4 ohm and must be firmly connected to ensure the
reliable discharge by lightning .
Sometimes the antenna can be installed outside the window, but the building must be
located in the open fields with no corner. In this way, it can receive at least half of the
satellite signal. But as a long-term using equipment , it is recommended that the antenna is
installed in high places, while the outside installation can be only adopted as a temporary
test .
The high-power microwave transmitting of the same band can not be around where the GPS
antenna is installed. In addition, we should try to avoid the GPS antenna from the direct
irradiation of high-power electromagnetic radiation.
I f the length of the feeder is less than 100 meters, the antenna and equipment can be
directly connected; between 100 meters to 200 meters, one more line amplifier is needed;
ranging from 200 meters to 300 meters, two more amplifiers are needed. If you need longer
feeder links, please contact us, GlobalTime Electronic Co., Ltd. We will provide the special
program to you. The feeder usually adopt 1 / 2 inch RF cable whose loss is 12.8dB/100m
from the United States Andrew's.
When setting up the feeder:
1. Do not bend too much, because it will result in a broken feeder conductor .
2. When we connect the feeder into the interior, it should be bent into U-shape to prevent t water
from flowing backward .
You can use GPS signal transponder to lead the signal to the interior. Generally speaking,
GPS signals can be well received within 5 m of the transponder antenna. Because of the

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way of forwarding, it is much effective for the prevention of lightning and the protection of the
host. Problems caused by the lightning is the transponder damaged. Due to a certain
transmitting power, it is suitable for some occasions.
Table 2-1 Antenna Specifications
Frequency range 1575 ± 5MHz; RF connector N-type connectors
Polarization
Right-hand circular
polarization
Installation
Thread (M24 × 1.5)
connection
Antenna gain
≥ 3.5dB
；
Volume
φ 96 × 126mm
；
Amplifier gain
≥ 37dB
；
Operating
temperature
-45
℃～
85
℃；
Noise coefficient
≤ 1.5dB
；
Storage
temperature
-50
℃～
90
℃；
Interference
suppression
25dB(f0 ± 100MHz)
；
Humidity
0
～
100%
Power consumption
3V × 20mA
；
2.3 I ndoor in s t allation
After connecting 220V AC to the master device, the indicator light "Power" on the front panel
will light which indicate s the running of power supply is normal. To measure the BNC
antenna socket with a mu l timeter, the feed voltage should be up to 5V .
Then connect the antenna cable with the antenna socket.
Next, use a computer to pass through the IP address and network settings of the serial port
configuration time server, save and exit, then restart GTT-200 Network time server to make
the network settings take effect. After reboot, input the IP address of the PING server in
another computer to check the network settings correct or not.
Last, log on the network time server through Telnet to observe the satellite receiving state,
the information on time tracking state of the server and so on. When the server locks the
satellite time ( The indicator light on the panel turns green), GTT-200 starts to provide time

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information to other clients within the network. The specific process of software configuration
can refer to the following chapter.
Chapter 3 Equipment m aintenance
3.1 Indicator state
Table 3-2 Indicator s tatus
Indicator Status Description
Power supply
on The power supply is normal
off The power supply is abnormal
NTP
off
The server is unlock and is searching for
the time source
green The time source is locked
GPS
off The satellite signal is not received
green The satellite signal is received
OCXO
off
No OCXO or not use OCXO for time
keeping
green Use OCXO to for time keeping
M/S
off Hot standby status
green The host status
3.2 The keyboard display
VFD display (vacuum fluorescent display), is of high brightness and wide vision. The screen
can display 20 ×2 characters. The line above shows the status while the line followed
shows the time.
When starting up, the system will show the company name: GlobalTime (about 15 seconds).
Then display: "Searching ... ... ... ... - or E", which shows that it is searching for the satellite.
After receiving the satellite signal, it will display: "Synchronizing ... ... ... .* ". The time will be
locked after 5-15 minutes and display: "Synchronized ... ... ... ..* ". "-" or "E" shown in the end
of the first line indicates not receiving the satellite signal and "*" indicates receiving the
satellite signal.