Digitally signed public certificates are required by the Autokey protocol. (See the interface at “Advanced: Keys/Certificates” on page 64.) All of this data goes into your certificate request (X.509) to a trusted Certificate Authority (CA). The CA can be an outside trust authority, such as VeriSign, or the device can certify itself. The S100 itself is
More details of the NTP protocol and synchronization techniques can be found in the Help file included with the interface, or at:
•http://www.ntp.org
•http://www.ietf.org/rfc/rfc1305.txt
S100 and the Global Positioning System
The Global Positioning System (GPS) receiver in the S100 tracks GPS satellites as they pass overhead and determines the range of the satellite in relation to its antenna. The GPS receiver uses the following four properties of the satellite to determine its own position and derive the time:
•x, or latitude
•y, or longitude
•z, or altitude
•t, or time
However, once the GPS receiver has calculated its position, only one satellite is needed to solve for time (t). This is because the receiver has tracked at least four satellites and has positioned itself. GPS time is expressed as the number of weeks since midnight, January 6, 1980 (GPS Week) and the number of seconds in the week. These two values are transmitted as binary integers from the satellites and converted into conventional date or day (UTC Time) by the GPS receiver.
S100 User Guide – Rev. D – June 2005 | 11 |
