Time synchronization

The realtime clock of the AlphaCom XE (as with any other computer device) is not accurate, and might drift over time. The clock will drift due to fluctuations in the frequency oscillating the quartz crystal on the AMC-IP board. The realtime clock can be synchronized in several ways.

NTP server

The AlphaCom can synchronize its real time clock with Network Time Protocol (NTP) time servers on the IP network. The syncronization is taking place once every hour. To activate the feature, define the IP address of a valid NTP server in the Time and Date settings in AlphaWeb.

If the AlphaCom is connected to the internet, you'll find a list of NTP servers here: http://support.microsoft.com/kb/262680

Synchronizing using a NTP server

The NTP uses port 123. This port must be opened on external firewall or router to ensure proper communication with the NTP server.

Calibrate the Realtime Clock

If there is no NTP Server available at site where the AlphaCom server is to be installed, there is an option to temporarily connect the AlphaCom to a network with NTP Server during commisioning (e.g. in the workshop before shipping to end customer). Configure the AlphaCom to syncronize the time to this NTP server. Now the AlphaCom clock will be compared to the NTP time, and a "drift file" will be created that contains an offset value. One should leave the AlphaCom connected to the NTP network for at least 24 hours to get the best value in the drift file. When the AlphaCom is moved to a network without NTP Server, it will use this offset value to correct the real time clock in AlphaCom.

To verify that the AlphaCom has calculated the drift, you can check from the Linux Console that the file "ntp.drift" contains a number value:

bash-3.2$ cat /var/run/ntp.drift
98.990

It may take a few hours from you define the NTP Server in AlphaWeb until the drift file "ntp.drift" is created

GPS network

GPS (Global Positioning System) is a world-wide satellite system that operates a time scale and transmits information for synchronizing to UTC (Coordinated Universal Time) with extreme high accuracy. The AlphaCom can syncronize its real time clock with a Master Clock which receives its time from GPS satelittes. The Master Clock 70000L has an embedded NTP server, to which the AlphaCom synchronizes.

Synchronizing using GPS network

Radio signal

DCF 77 signals transmitted from Germany is the most frequently used signal in Europe. The signal is sent every minute and comprise minute, hour, year and date.

In France the national TDF transmits signals for time synchronization and in Great Britain the MSF-Rugby sends similar signals for synchronization. RDS is a signal transmitted over the FM band in Scandinavia.

Many other European countries have national signal system which includes time data and which can be used for time synchronization.

Close contact

If the AlphaCom gets a contact closure at a fixed time once a day, the contact can be connected to a Remote Control Input RCI, which can be configured to set the time using the $SST command.

When RCI 1 is activated, set the time to 04:30:00

Via the ACDP protocol

The clock of the AlphaCom can be set from external equipment (PC, Management System etc.) communicating with the AlphaCom over the ACDP protocol.

The message SET SYSTEM TIME ($SST) is used for this purpose.