GPSPCI 2/72008 Rev 1.2.1
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Masterclock, Inc.
INTRODUCTION
The GPSPCI is a PCI card that provides very stable accurate time and date information for a
Windows PC. The card receives reference time information from Atomic Clocks in the GPS
(Global Positioning System) satellites.
GPS SATELLITES
The GPS satellites are operated and maintained by the US Department of Defense and allow for
the precise determination of local time and location at any point on (or above) the Earth. This is
accomplished via the transmission of very accurate timing information from a series of satellites
that provide coverage of the entire planet.
The GPSPCI extracts timing reference from these signals and generates time information to the
PC that is synchronized to within less than 10 microseconds of UTC (Universal Coordinated or
Greenwich Mean Time).
UTC/GREENWICH MEAN TIME
UTC is the local time at the prime reference meridian at Greenwich, England. At a given
location on the planet, local time can be displaced (referenced to UTC) by -11 to +12 hours.
North and South America are from -3 to -11 hours delayed; most of Europe and Africa and all of
Asia and Australia are advanced by +1 to +12 hours.
TIME ZONES & DAYLIGHT SAVING TIME
The GPSPCI provides UTC to the PC’s operating system. Time zone offsets and daylight
savings time are handled as a standard feature of the operating system.
INITIAL OPERATION
Each GPSPC is thoroughly tested with its external antenna prior to shipment. Physical
installation is simply a matter of installing the card into a PCI or ISA bus slot and connecting the
antenna.
OPERATING THE GPSPCI FOR THE FIRST TIME
When the GPSPCI is initially powered up, after having been shipped to a new location, the time
to first fix (time the unit takes to acquire satellites and extract correct time) could be up to 25
minutes although it is typically 5 - 15 minutes. Factors such as atmospheric conditions, antenna
type, antenna location, and antenna cable length will affect the time to first fix.
The GPSPCI will provide time from an internal on-board clock whenever GPS time is not
available. The onboard clock runs from a backup battery in the absence of power from the PC.
