Brandywine NFS-221 User manual

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MANUAL P/N 900000113 REV A
User Guide
Networked Frequency Standard
Model NFS-221
P/N 091001001
Revision B
November 2011
Brandywine Communications
1153 Warner Ave
Tustin, CA 92780
[phone]
[phone]
http://www.brandywinecomm.com

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MANUAL P/N 900000113 REV A
Revision History
REVISION DATE COMMENTS
A 04-30-2009 Original release of NFS-221 User Guide.
B 11-03-2011 1 PPS Input level amendment

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MANUAL P/N 900000113 REV A
Safety Warnings
WARNING: This unit contains lethal AC voltages. Disconnect the unit from
the AC supply before removing the cover.
WARNING:
The lightning flash with an arrowhead inside of an equilateral triangle is intended to alert the
user to the presence of un-insulated “dangerous voltage” within the product’s enclosure. The
“dangerous voltage” may be of sufficient magnitude to constitute a risk of electrical shock to
people. Do not attempt to repair the unit without first unplugging it.
CAUTION:
The exclamation point inside of an equilateral triangle is intended to alert the user to the
presence of important operation and maintenance instructions in the user guide. This unit
should only be repaired by qualified personnel. Several board assemblies contain static
sensitive devices. Appropriate procedures must be used when handling these board
assemblies.

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MANUAL P/N 900000113 REV A
Table of Contents
1Introduction..................................................................................................................................5
2Specifications ..............................................................................................................................6
2.1 LED Indicators ....................................................................................................................8
2.2 Connections........................................................................................................................9
2.3 Source Impedance Selection and Signal Termination .....................................................10
3Unpacking and Installation ........................................................................................................10
3.1 Unpacking.........................................................................................................................10
3.2 Installation ........................................................................................................................10
3.2.1 Mounting ......................................................................................................................10
3.2.2 Power ...........................................................................................................................11
3.2.3 Ethernet........................................................................................................................11
3.2.4 Input Reference Connections.......................................................................................11
3.2.4.1 GPS Antenna.......................................................................................................11
3.2.4.2 External GPS Receiver (Have Quick/1PPS)........................................................12
3.2.4.3 External 1PPS Receiver ......................................................................................13
3.2.5 NTP Server Connection Example.................................................................................13
3.3 Output signal connections ................................................................................................13
3.3.1 Signal Connections ......................................................................................................13
3.3.2 Network Connections ...................................................................................................13
3.3.2.1 Discovering the automatically assigned NFS-221 IP address..............................14
3.3.2.2 Changing NFS-221 Network IP address using Internet Explorer.........................14
3.3.2.3 Latest Version of Java Software ..........................................................................16
4Configuration .............................................................................................................................17
4.1 Setup ................................................................................................................................17
4.1.1 System .........................................................................................................................18
4.1.2 IP Address....................................................................................................................18
4.1.3 Reference.....................................................................................................................18
4.1.4 Application....................................................................................................................18
4.1.4.1 GPS Fixed Location Application ..........................................................................18
4.1.4.2 GPS Mobile Application.......................................................................................19
4.1.5 Manual Time Set ..........................................................................................................19
4.2 Status ...............................................................................................................................20
4.2.1 Local Time....................................................................................................................20
4.2.2 Reference Status..........................................................................................................21
4.2.3 Oscillator Status ...........................................................................................................21
4.2.4 Fault Status ..................................................................................................................21
4.3 Time..................................................................................................................................22
4.3.1 Serial Output (TOD) .....................................................................................................23
4.3.2 Time Zone Settings ......................................................................................................24
4.3.2.1 Standard Time Zone settings...............................................................................24
4.3.2.2 Special case – 30 minute time zone setting.........................................................24
4.3.3 Daylight Saving Time ...................................................................................................25
4.3.4 Daylight Saving Time (Advanced) ................................................................................25
4.4 Password..........................................................................................................................26
4.4.1 Password......................................................................................................................26
4.5 Help ..................................................................................................................................27
5Drawings ...................................................................................................................................28

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MANUAL P/N 900000113 REV A
1Introduction
The NFS-221 is a precision time and frequency standard that uses the Global Positioning System
(GPS).
It is designed for use in WI-FI, Wi-Max, satellite communications, telecommunications and military
communication applications.
The NFS-221 utilizes a high performance 16 channel GPS receiver. An automatic position-averaging
feature enables the best use of GPS when operating in a fixed location.
The NFS-221 is fitted with an internal back up oscillator that is continuously calibrated to GPS using
an advanced algorithm, providing optimal frequency control of the oscillator. This ensures that the
highest time and frequency accuracy is maintained if no satellites can be tracked, and ensures an
ultra stable, low noise frequency reference.
The basic NFS-221 includes a precision OCXO frequency standard, while TCXO and Rubidium
oscillators are available options that offer a variety of price and performance options. An option with a
low noise OCXO phase locked to a Rubidium is also available, combining the low noise characteristic
of the OCXO with the long term stability of a Rubidium oscillator.
The NFS-221 provides “at a glance” status indication via front panel LED’s and can be integrated
with other management systems using Ethernet and serial ports.
The NFS-221 generates 1PPS signals compatible with ICD-GPS-060.
The integrated Ethernet interface provides Network Time Protocol (NTP) synchronization to other
connected computers. In addition to NTP, the NFS-221 Ethernet interface contains a built-in web
server that allows the NFS-221 to be controlled using a standard web browser such as Internet
Explorer. Simple Network Management Protocol (SNMP) allows easy integration of the NFS-221
with industry standard network management systems.
The NFS-221 provides eleven 1PPS time mark outputs. A unique feature allows precise controlled
delays to be inserted into these outputs to compensate for cable- and other propagation delays.
Compensation delay is independent for each output and has <1ns resolution.
Serial time code outputs are provided to allow time synchronization to be distributed to computers,
displays, and other equipment requiring precision time.
All outputs are provided with activity detectors. Loss of any output is indicated by means of an
individual front panel alarm LED as well as through the network interface or a discrete alarm output.

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MANUAL P/N 900000113 REV A
2Specifications
Reference Inputs
GPS
Receiver Type Parallel 16 Channel. All-in-view satellites tracked continuously and
simultaneously
Satellite Signal GPS L11575.42 MHz
Satellite Code C/A 1.023 MHz
Warm Start <10 sec(Open Sky)
Autonomous Start <60 seconds Cold Start (Open Sky)
Cold Start Requirement Automatic: No input of time or position required
Position Accuracy 2.4 m horizontal, 5 m altitude with respect to WGS84 after 24 hour position
averaging
Antenna Connector BNC Female
Have
Quick
Signal Type Have Quick II per ICD-GPS-060
Input Impedance 50 ohm
Level 0-5V
TFOM Threshold 4
Connector BNC Female
External
1PPS
Signal Type 1PPS
Input Impedance 50 ohm
Level Logic 0: 0 .4 V max
Logic 1: 2.5V min and 5.0V max
Maximum Frequency
Error
2x10-9
Connector BNC Female
Input Modes
GPS Default
Have Quick/1PPS Uses 1PPS for synchronization, Time of Day is loaded automatically from
Have Quick
External 1PPS only Uses 1PPS for synchronization, Time of Day is loaded manually by user
System Accuracy
Specifications are based on GPS mode tracking satellites unless noted.
Timing Accuracy
±100 ns. absolute UTC
Std Deviation 15ns (OCXO)
Timing Accuracy
(holdover mode, ± 5ºC)
< 25 μsec/day (OCXO)
< 2 μsec /day (Rb2)
Frequency stability) See tables below
Oscillator Option Stability
-10 to 50 °C
Allan Variance
1s 10s 100s 1000s 10000s 1 day
TCXO 2.5x10-6 1x10-7 1x10-7 1x10-7 5x10-8 2x10-9 1x10-11
OCXO (std) 3x10-9 5x10-12 8x10-12 1x10-11 1x10-11 5x10-12 1x10-12
Rb1 7x10-10 3x10-11 1.6x10-11 8x10-12 <1x10
-12
Rb2 4x10-10 1x10-11 3x10-12 1x10-12 <1x10
-12
Rb/OCXO 4x10-10 5x10-12 1x10-11 3x10-12 <1x10
-12

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MANUAL P/N 900000113 REV A
System Outputs
1PPS Output 11 Outputs
Connector BNC (8) DB9 (3)
Level 0-10V for output 1 to 8 (BNCs)
0-5V for output 9, 10, 11. (DB9)
On Time Rising Edge
Width 100ns to 6.5 ms software settable in 100ns steps
Delay -0.5 to +0.5 seconds in 1 ns steps
Individually settable for each output
Network Interface
Interface Type 10BaseT
Protocols TCP/IP, UDP, NTPv3, HTTP, SNMP v1, DHCP
Serial Interface
Type RS232
RS422 link selectable by user
Baud rate 115200, N,8,1
Alarm Status Voltage free relay changeover contacts. Link settable for +5V alarm out
Status Indicator LED’s Power
Tracking Satellites
Valid Time
Holdover/12hr Holdover alarm
Output Good/Fail ( 8 LEDs)
Environmental
Temperature Instrument: -10 to +50 °C
Antenna: -40 to +85 °C
Humidity 95% non condensing
Power 85-265VAC 50/60Hz
Optional 12VDC, 24VDC, -48VDC, 125VDC
Dimensions 19” rack mount
1.75” (1U) height, 6.5“ depth
Weight 3.5 lb. typical
EMC Emission EN55022
FCC Chapter 15 Subpart B, Class A
EMC Immunity EN55024

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MANUAL P/N 900000113 REV A
2.1 LED Indicators
Table 1 below describes each LED indicator on the front panel of the NFS-221.
LED COLOR COMMENT
Power Green Indicates Prime Power is applied to the NFS-221.
Time Valid Green Indicates that the unit has been synchronized to an external reference.
Amber Indicates that the unit is in Holdover.
Tracking
Satellites
Green Indicates that the GPS receiver is tracking satellites OR that the Have
Quick time code has been successfully decoded if HQ is selected as a
reference.
Red Indicates that the NFS-221 has not had a valid reference for 12 hours.
Off Indicates that the NFS-221 is not tracking satellites or successfully
decoding HQ.
1PPS
J1
Green Indicates that the 1PPS pulse output on J1 is operating.
Red Indicates that the 1PPS pulse output on J1 has failed or that there is
an excessive load on the output.
1PPS
J2
Green Indicates that the 1PPS pulse output on J2 is operating.
Red Indicates that the 1PPS pulse output on J2 has failed or that there is
an excessive load on the output.
1PPS
J3
Green Indicates that the 1PPS pulse output on J3 is operating.
Red Indicates that the 1PPS pulse output on J3 has failed or that there is
an excessive load on the output.
1PPS
J4
Green Indicates that the 1PPS pulse output on J4 is operating.
Red Indicates that the 1PPS pulse output on J4 has failed or that there is
an excessive load on the output.
1PPS
J5
Green Indicates that the 1PPS pulse output on J5 is operating.
Red Indicates that the 1PPS pulse output on J5 has failed or that there is
an excessive load on the output.
1PPS
J6
Green Indicates that the 1PPS pulse output on J6 is operating.
Red Indicates that the 1PPS pulse output on J6 has failed or that there is
an excessive load on the output.
1PPS
J7
Green Indicates that the 1PPS pulse output on J7 is operating.
Red Indicates that the 1PPS pulse output on J7 has failed or that there is
an excessive load on the output.
1PPS
J8
Green Indicates that the 1PPS pulse output on J8 is operating.
Red Indicates that the 1PPS pulse output on J8 has failed or that there is
an excessive load on the output.
Ethernet
J11
Yellow Activity
Green Link
Table 1 LED Indicators

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2.2 Connections
Table 2 shows the signal interface connections provided on the NFS-221.
CONNECTOR REFERENCE CONNECTOR
TYPE CONNECTOR PIN SIGNAL
J1 1 PPS OUTPUT 1 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J2 1 PPS OUTPUT 2 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J3 1 PPS OUTPUT 3 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J4 1 PPS OUTPUT 4 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J5 1 PPS OUTPUT 5 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J6 1 PPS OUTPUT 6 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J7 1 PPS OUTPUT 7 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J8 1 PPS OUTPUT 8 BNC FEMALE CENTER 1 PPS
SHIELD GROUND
J9 INPUT/OUTPUT DB-9 FEMALE 1 NO CONNECTION
2 1 PPS OUTPUT 10
3 1 PPS OUTPUT 11
4
A
LARM OUT NORMALLY CLOSED CONTACT
5
A
LARM OUT NORMALLY OPEN CONTACT
6 GROUND
7 1 PPS OUTPUT 9
8 GROUND
9
A
LARM OUT COMMON
J10 CONSOLE PORT DB-9 MALE 1 HAVE QUICK INPUT (EXTERNAL REFERENCE)
2 RS232 RECEIVE DAT
A
3 RS232 TRANSMIT DATA (SERIAL DATA)
4 1PPS INPUT (EXTERNAL REFERENCE)
5 GROUND
6 RS422 RECEIVE DATA -
7 RS422 RECEIVE DATA +
8 RS422 TRANSMIT DATA
–
(SERIAL DATA)
9 RS422 TRANSMITDATA + (SERIAL DATA)
J11 ETHERNET RJ-45 1 TX+
2 TX-
3 RX+
4 -
5 -
6 RX-
7 -
8 -
J12 ANTENN
A
BNC FEMALE CENTER GPS L1, +5V power for antenna
SHIELD GROUND
Table 2 Interface Connections

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2.3 Source Impedance Selection and Signal Termination
Signal/Connecto
r
Connecto
r
Link Setting Source Impedance Recommended Load
Impedance Factory Setting
1PPS 1 J1 LK5 on Low Z 50 ohm
LK5 off 50 ohm 50 ohm
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1PPS 2 J2 LK6 on Low Z 50 ohm
LK6 off 50 ohm 50 ohm
9
1PPS 3 J3 LK7 on Low Z 50 ohm
LK7 off 50 ohm 50 ohm
9
1PPS 4 J4 LK5 on Low Z 50 ohm
LK5 off 50 ohm 50 ohm
9
1PPS 5 J5 LK6 on Low Z 50 ohm
LK6 off 50 ohm 50 ohm
9
1PPS 6 J6 LK7 on Low Z 50 ohm
LK7 off 50 ohm 50 ohm
9
1PPS 7 J7 LK6 on Low Z 50 ohm
LK6 off 50 ohm 50 ohm
9
1PPS 8 J8 LK7 on Low Z 50 ohm
LK7 off 50 ohm 50 ohm
9
Table 3 Source Impedance and Recommended Signal Terminations
3Unpacking and Installation
3.1 Unpacking
Remove the NFS-221 from the shipping carton. The following items should be included in the
shipment:
•1 NFS-221
•1 GPS antenna
•1x 100 feet of coaxial antenna cable
•1 user guide (CD-ROM)
3.2 Installation
3.2.1 Mounting
The NFS-221 can be installed into a 19” rack mount cabinet either using rack slides or only using the
front panel flanges. For static applications, the short depth and light weight of the NFS-221 ensures
that the front panel is not stressed when only the front panel is used for support.
If the NFS-221 is installed on a mobile platform and must survive shock and vibration, the use of
slides is recommended. Slides are installed using 10-32 UNF-2B hardware.
Optional Rack Mount Slides:
P/N 002000123, SLIDE, RACK, 24", 21" TRAVEL, 85 LB
P/N 002000150, SLIDE, RACK, 28", 27" TRAVEL, 80 LB
Original Manufacturer: General Devices Chassis Trak Type C300.

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MANUAL P/N 900000113 REV A
3.2.2 Power
Insert the power cord of the NFS-221 into an electrical socket to power up the unit. The Power LED
indicator will illuminate green.
3.2.3 Ethernet
Connect one end of an Ethernet patch cable to the NFS-221 Ethernet port J11. Connect the other
end of the Ethernet cable to your network with an Ethernet hub or switch.
3.2.4 Input Reference Connections
3.2.4.1 GPS Antenna
Connect the GPS antenna to the J12 Antenna BNC connector on the rear panel of the unit. The
GPS antenna must be located in a suitable location with a clear view of the sky. In most cases, the
GPS signals do not penetrate buildings. Use the cable provided in the shipment to connect the GPS
antenna and NFS-221. In the event that a longer cable is required, a low loss cable must be used so
that the total signal attenuation at 1575 MHz is < 20 dB. For more information on suitable cables
contact Brandywine Communications.
Location
Several factors need to be considered when installing the GPS antenna. In most cases, the antenna
is mounted externally (outdoor) and exposed to the elements. A good quality coaxial cable of 50
ohm impedance is required to connect the GPS antenna to the NFS-221. The cable provides two
functions, which are to conduct the GPS RF signals (1575.42 MHz) that are received from the GPS
antenna to the NFS-221 and to conduct the DC bias voltage (5 VDC) provided by the NFS-221 to the
LNA (low noise amplifier) contained inside of the GPS antenna. The antenna should be mounted
securely, with a clear view of the sky, and with the top of the antenna pointing upward. In some
installations it may not be possible to mount the antenna such that the antenna has a clear 360
degree view of the sky. In such cases pick the location with the best view of the sky.
Exposure to High RF Fields
Some installations may occur in locations where a variety of high power transmitters and antennas
are located. The GPS antenna should not be directly exposed to or bombarded with high level RF
energy. In such cases, the antenna should be located either above, below, or to the side of these
high power RF transmission antennas.
Lightning Protection
The NFS-221 does not provide any inherent protection against lightning strikes. In general, lightning
protection (when desired or needed) is provided by an externally mounted protection device that is
designed to shunt the high voltage transient to a well established earth ground. Lightning arresting
devices designed for use with the GPS antenna system are available at Brandywine Communications
(P/N 001000914).

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MANUAL P/N 900000113 REV A
RF Loss
The most important source of signal loss is the RF signal attenuation experienced in the cable. The
amount of attenuation is related to the type (quality) of coaxial cable and cable length. The antenna
provides about 30 dB of gain to the received GPS signal. The purpose of this gain is to offset the
loss that is experienced in the cable between the GPS antenna and NFS-221. It is recommended
that the overall antenna system gain (antenna gain - cable loss) be between 10 dB - 33 dB. Using an
antenna with 30 dB of gain allows for about 20 dB of cable loss. The NFS-221 is shipped with 100’ of
Belden 8240 antenna cable with a cable loss of approximately 18 dB. For distances beyond 100’,
Brandywine recommends low loss Belden 9914 with a loss of 5.84 dB/100ft
Standard antenna cable using this configuration is available from Brandywine as shown in Table 4.
For distances beyond 330’, an in-line amplifier is required.
Tempest Facilities/Extremely Long Cable Runs
For applications where no conductive penetration of EMC shielding can be tolerated or for extremely
long cable runs, Brandywine Communications offers a remotely powered fiber optic antenna link.
This comprises two external units. The remote down-converter and fiber unit is connected to the
antenna and it converts the GPS RF signal to an optic signal at lower frequencies that is suitable for
transmissions over a fiber optic cable. The local fiber and up-converter unit accepts the optical signal
and converts it back into an electrical RF signal that is processed by the NFS-221.
PART NUMBER CABLE LENGTH CABLE TYPE
002-0037 100 feet RG58 (supplied)
002-0040 150 feet RG8
002-0052 250 feet RG8
002-0039 330 feet RG8
051000001 In-line amplifier 20 dB TNC/TNC connectors
002-0065 Fiber optic cable converter up to
1500 meters
Multi-mode fiber optic
Table 4 NFS-221 Antenna Cable options
3.2.4.2 External GPS Receiver (Have Quick/1PPS)
The NFS-221 can also be synchronized to an external GPS receiver such as the AN/PSN-13
Defence Advanced GPS Receiver (DAGR), or AN/PSN-11 PLGR .
Both of these receivers incorporate a 1PPS Time Mark and Have Quick time code output that are
used by the NFS-221 as references. Both signals are required for automatic operation. The NFS-221
requires that the TFOM is ≤4 before it will accept the time.
The cable connections to the NFS-221 are shown in Table 5 and Table 6:
AN/PSN-13 DAGR Signal Name Direction NFS-221 (J10)
J2-7 Have Quick > 1
J2-6 1PPS > 4
J2-11 Signal Return > 5
Table 5 Cable Connection to DAGR

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MANUAL P/N 900000113 REV A
AN/PSN-11 PLGR Signal Name Direction NFS-221 (J10)
7 Have Quick > 1
6 1PPS > 4
11 Signal Return > 5
Table 6 Cable Connection to PLGR
3.2.4.3 External 1PPS Receiver
The NFS -220 can also be synchronized to an external receiver that incorporates a 1PPS Time Mark
only as a reference. An accurate manual time entry is necessary in this case. See section Error!
Reference source not found.
3.2.5 NTP Server Connection Example
The NFS-221 is suitable for use as a Network Time Server, supporting Network Time Protocol (NTP).
An example of the deployment of the NFS-221 in this role is shown below.
Figure 1 Typical NFS-221 NTP Server Network Connection
3.3 Output signal connections
3.3.1 Signal Connections
The output signals from the NFS-221 should be connected as required using appropriate
connectors/cables. The cable should be terminated in the impedance shown in Table 3 for optimum
operation. In particular, the 1PPS signal has very fast rise times, and to prevent unwanted reflections,
these outputs should be terminated correctly in 50 ohm
All BNC connectors are 50 ohm.
3.3.2 Network Connections
The NFS-221 is shipped with a DHCP enabled IP address stored in the unit.
To change the network address, the user may use a web browser.
Workgroup
Switch
NFS-221 LAN Enterprise Server
(NTP Stratum 2)
NTP
Clients
Local NTP
Clients

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MANUAL P/N 900000113 REV A
3.3.2.1 Discovering the automatically assigned NFS-221 IP address
In the default configuration, the NFS-221 is automatically assigned an IP address by the network’s
DHCP server. In order to use a web browser to control the unit, this address must be discovered.
This can be done by connecting a computer to the NFS-221 console port J10, via RS232, and using
a terminal program such as HyperTerminal or Tera Term.
1. Configure the terminal program to accept ASCII data at 115,200 baud, No Parity, 8
bits/character, 1 stop bit (115200, N, 8,1); No Flow Control.
2. Cycle Power to the NFS-221.
3. A short string will be broadcast by the NFS-221 that has the IP address of the unit.
4. Note that in the example shown in Figure 2 the IP address is 192.168.1.118 which is the new
address that the DHCP server assigned to it upon power up.
Figure 2 NFS-221 console port start-up string
3.3.2.2 Changing NFS-221 Network IP address using Internet Explorer
Enter the IP address of the NFS-221 into the address bar of a web browser running on a computer
that is connected to the same network as the NFS-221, as shown in Figure 3
Figure 3 Browser settings for NFS-221
The browser page for the NFS-221 will load. Select the tab for Setup, as shown in Figure 4.

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MANUAL P/N 900000113 REV A
Figure 4 Setting IP address through the browser
1. Check the Box to Disable DHCP
2. Enter the desired parameters for the device IP address, the Subnet Mask and the gateway.
If you enter an invalid IP address, subnet mask and gateway, you may not be
able to reach the NFS-221 using a web browser. Carefully check this information prior to
entry, and check with your network administrator for the correct settings.
3. Click on the Submit button.
4. Note that the browser will not reload the page, because the NFS-221 IP address has now
changed.
5. Set the browser to the newly configured IP address and confirm that the NFS-221 IP address
has changed as desired.

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MANUAL P/N 900000113 REV A
3.3.2.3 Latest Version of Java Software
To properly control and monitor the NFS-221 via a web browser based interface, Java software must
be installed on your computer. To obtain the Java software, follow the steps given below.
1. Go to http://www.sun.com/ .
2. Click on the Downloads link.
3. Click on the Java Download link.
4. Download Java.
5. Complete the installation process.
Please note that the oldest acceptable Java software version number is 1.4.2_05. To check the Java
software version number installed on your computer, follow the steps given below.
1. Go to ‘Start’.
2. Go to ‘Control Panel’.
3. Go to ‘Add or Remove Programs’.
4. Scroll through the ‘Currently installed programs’ list.
5. Locate the ‘J2SE Runtime Environmental’ program.
6. The version number follows the program’s name in step 5.

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MANUAL P/N 900000113 REV A
4Configuration
Please note that the unit will automatically reboot when a serious error or lock up occurs. This allows
the unit to reset and run instead of locking up.
4.1 Setup
The Setup tab consists of five sections, the System, IP Address, Reference, Application and Manual
Time Set. This tab allows you to modify setup information for the NFS-221. Please note that a Class
C Network is being used therefore valid IP addresses are between 192.0.0.0 to 223.255.255.0. To
save all modifications made to the Setup screen, click the Submit button. To undo all modifications
made to the Setup screen, click the Reset button.
Figure 5: Setup

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MANUAL P/N 900000113 REV A
4.1.1 System
The System section consists of two fields, the Version and Unit Location. The Version refers to the
version number of the firmware. The Unit Location refers to the location of the unit. A maximum of
127 characters may be entered in the Unit Location field. Entering apostrophes (‘) in the Unit
Location field is not recommended.
4.1.2 IP Address
The IP Address section consists of two radio buttons, the DHCP Enable and DHCP Disable and
three fields, the Device IP Address, Device Subnet Mask, and Device Gateway. If the DHCP Enable
radio button is selected, the NFS-221 will retrieve its configurations from the DHCP server. If the
DHCP Disable radio button is selected, the user must manually enter the configurations for the
device.
The Device IP Address is a 32-bit number that identifies the device on an IP network. The Device
Subnet Mask is a 32-bit number that enables the user to define sub-networks. The Device Gateway
is a 32-bit number used as the point of entrance from one network to another.
4.1.3 Reference
The Select reference pull down menu allows the user to select one of three reference types to
acquire time from. The only references used by the system are GPS, Have Quick & 1PPS, and
1PPS.
Figure 6 Selecting the NFS-221 reference
Select the Reference type desired and click the Submit button.
4.1.4 Application
In this mode, an internal 16 channel GPS receiver is used as the system reference. The NFS-221
operates automatically in acquiring and tracking all GPS satellites in view. If the GPS receiver is
selected, then a secondary selection should be made to determine whether the NFS-221 is being
used in a stationary or mobile application.
4.1.4.1 GPS Fixed Location Application
If the fixed location mode is selected, the NFS-221 will begin to survey it’s location by collecting and
averaging the position that it computes from the GPS satellites. The averaged position is then stored
into the GPS receiver, and the receiver transitions to a timing mode, where the averaged position is
assumed correct, and time is only calculated from all satellites in view. Erroneous satellite tracking
data can be detected and removed from the over-determined timing solution using the receiver’s built
in Receiver Autonomous Integrity Monitoring (RAIM) function. In locations where the satellite visibility
is poor, the NFS-221 can operate with as few as 1 satellite when in the timing mode.

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MANUAL P/N 900000113 REV A
Figure 7 GPS Fixed/Mobile Selection
4.1.4.2 GPS Mobile Application
If the Mobile Application mode is selected, the internal GPS receiver will not perform any position
averaging, and will continuously compute both position and time from all satellites in view. The RAIM
function is still active, but requires a minimum of 5 satellites tracked to provide fault detection and
isolation.
4.1.5 Manual Time Set
If the External 1PPS Only mode is selected then the NFS-221 will synchronize to the external 1PPS
appearing on J10-4. The epoch of this 1PPS must be manually entered by entering the time of the
next second using the function provided. Prior to the next second, click Submit to load
the time into the NFS-221.
Figure 8 Manual Setting of Time in NFS-221
In this mode the external 1PPS will always be used as the reference to which the internal oscillator is
steered, so that it is critical that the 1PPS comes from a high stability, highly accurate source.

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MANUAL P/N 900000113 REV A
4.2 Status
The Status tab consists of four sections Local Time, Reference Status, Oscillator Status, Fault
Status. This tab allows you to monitor the functional status of the NFS-221. There are no functions
that can be modified on this tab – it is all read-only information.
Figure 9: Status
4.2.1 Local Time
This section displays the local time of the NFS-221. This display updates the current time each
second.