Specifications

Masterclock, Inc.
January
phone (USA and Canada): 1-800-940-2248 | phone (international): [phone]
email: [e-mail] | online: www.masterclock.com
SUGGESTED FUNCTIONAL SPECIFICATION for a GPS Synchronized Clock System using
Network Time Protocol and Power over Ethernet
1.1 SCOPE
This document specifies a wired clock system that relies on the accuracy of the Global Positioning
Satellite (GPS) system for synchronizing the time provided to clocks and network devices using the
Network Time Protocol (NTP). Such a clock system relies on one or more NTP time servers with an
integrated GPS receiver, to act as master clocks and virtually an unlimited number of network clock
displays acting as client devices. In addition, other network client devices can benefit from the
availability of the NTP timeservers. Data and low voltage DC power can be distributed over the
same network cable using Power Over Ethernet technology, resulting in significant cost savings. The
limitations are primarily network configuration and implementation based, as the system can be
added to an existing network or configured as an independent network to simply provide a
synchronized clock display system.
1.2 GENERAL
NTP (Network Time Protocol) servers allow clients to synchronize clocks, bells, computer clocks,
other computer timing devices and other kinds of network equipment using a standard reference of
time accepted worldwide, known as UTC (Universal Time Coordinated).
NTP servers with an integrated GPS receiver located on a LAN (Local Area Network) can provide the
high accuracy of the GPS satellite system to provide the UTC reference time, eliminating the need to
receive time from a NTP server located on the Internet. Placing one or more NTP on your local
network behind your facilities firewall enhances reliability, redundancy, accuracy, and security.
Using NTP is clearly an advantage since it permits automatic synchronization of all the equipment
hooked up to the network, thus reducing the need and associated cost for personnel to travel to
remote clock locations to set the time manually.
In general, it has been observed that since the recent introduction of NTP as a standard for network
synchronization, clock installations have become easier, better synchronized, more reliable, and
provide a traceable source of time for critical network functions, resulting in lower overall cost.
NTP provides a simplified protocol called SNTP (Simplified Network Time Protocol), which clients
can utilize to set the time to trusted NTP timeservers. SNTP V4 is a subset of the full NTP V3 version
and is widely accepted for client devices.
POE (Power over Ethernet) is a recognized and a growing method of significantly reducing
installation costs and providing low voltage DC power to network devices by distributing power
over the unused pair of standard network cables. The modest incremental cost of purchasing POE
equipment that is compliant to the IEEE 802.3af standard, dramatically offsets the installation costs
and safety issues associated with utilizing and distributing AC power.
A GPS Synchronized clock system using NTP and POE offer significant installation and maintenance
cost benefits over traditional clock systems.
Information
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ested Functional Specs.
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