Software Drivers to Use With Praecis II

To turn your existing server into a Stratum 1 network time server you need the Praecis II and existing, public-domain NTP software and drivers available for Unix, Linux, Solaris and Windows platforms.  A Stratum 1 network time server is a networked computer connected to an external source of accurate time, such as Praecis II.  The computer synchronizes its clock to the external source of time and provides accurate time-of-day information to the clients on the network.  The Network Time Protocol (NTP) was developed by Dr. David Mills and is freely distributed at the official NTP web site:

Go to to see a list of all external reference clocks with existing NTP driver support.  The Praecis II outputs an ASCII time-of-day message string on the serial port once per second.  It can easily be configured to mimic the string format of several different reference clocks with existing drivers.  Clock choices available are: TrueTime, Trimble Palisade, and Spectracom.  These drivers are available for Unix, Linux and Solaris platforms.  Simply configure the Praecis II to mimic the clock of your choice, and then download and compile a recent release of the NTP distribution which includes the reference clock drivers.

The Praecis II is a second generation product (first generation was called Praecis Ct).  At the NTP Public Services Project there is help which describes the steps needed to set up a Praecis Ct as a refclock on FreeBSD/Linux/Unix.  Instructions are identical for the Praecis II.  Go to for "Installing an EndRun Praecis Ct CDMA Based Refclock".

For the utmost precision on Windows NT/2000/XP, the Praecis II is compatible with the Trimble Palisade driver for use with the NTP distribution.  In this mode, the Praecis II timetags the assertion of the RTS handshaking signal sent by the Windows machine and returns the timetag in a format that is compatible with the Trimble Palisade driver.  For a compiled version of the NTP gui install for NT/2000/XP/Server2003 go to the Microsoft Windows section at this link: