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<concept id="GUID-A5510456-A5EB-59EC-B146-74D58A118875" xml:lang="en"><title>LBS

System Clock Synchronisation Overview</title><shortdesc>This topic describes how LBS synchronises the system clock with

time data received as part of the GPS signal. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section><title>Introduction</title> <p>The GPS signal contains accurate time

data. LBS can use this data to synchronise the system clock with GPS. The

system clock is synchronised with GPS at regular intervals if the difference

between GPS time and the system clock time exceeds a threshold time difference. </p> </section>

<section><title>Key concepts</title> <dl>

<dlentry>

<dt>System clock</dt>

<dd><p>The mobile device clock that keeps system time. </p> </dd>

</dlentry>

<dlentry>

<dt>Set clock plug-in DLL</dt>

<dd><p>An optional licensee ECom plug-in DLL used by LBS to set the system

clock. Symbian provides a default class that sets the system clock by calling <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita#GUID-C197C9A7-EA05-3F24-9854-542E984C612D/GUID-145F52E6-2A29-3FF1-8AD1-7009BE0074D7"><apiname>User::SetUTCTime()</apiname></xref>. </p> <p>It

is only necessary to implement a set clock plug-in DLL if a licensee requires

to set the system clock by some means other than by calling <codeph>User::SetUTCTime()</codeph>. </p> <p>Whether

LBS uses a plug-in DLL or the Symbian default class is configured through

the <xref href="GUID-23BBC1D8-B3A0-5148-A4F1-22ECF3043E4E.dita">LBS administration

service</xref>. </p> </dd>

</dlentry>

<dlentry>

<dt>UTC</dt>

<dd><p>Co-ordinated Universal Time. A worldwide time standard. UTC is derived

from the GPS signal and is the time standard used to set the system clock. </p> </dd>

</dlentry>

</dl> </section>

<section><title>API Summary</title> <p>There are two separate APIs involved

with LBS system clock adjustment: </p> <ul>

<li id="GUID-C8F1C9F9-E1D8-5F93-B6EC-6FDA8D81D5E8"><p>The LBS Set Clock Plug-in

Interface </p> <p>Licensees can derive from the interface to create an implementation

class. The class is packaged as an ECom plug-in DLL which is loaded at startup

and used to set the system clock. </p> </li>

<li id="GUID-ED0758AB-DC45-5EE7-97D3-FFAA9CB1CE3E"><p>Automatic clock synchronisation </p> </li>

</ul> </section>

<section><title>The LBS Set Clock Plug-in Interface</title> <p>LBS defines

an interface class that is used to create a set clock plug-in DLL. </p> <p>The

interface <xref href="GUID-E5ED4ACA-5EC4-3AE2-862A-AC204DCA83B5.dita"><apiname>CGPSSetClockBase</apiname></xref> is shown in figure 2. </p> <fig id="GUID-EEA7FD08-77F2-563F-BD94-DC74DC1A96DE">

<title>              Figure 2. CGPSSetClockBase is the interface for LBS set

clock plug-in              classes.            </title>

<image href="GUID-9BA295BC-627C-5B82-B669-F4F7B55E3F82_d0e459070_href.png" placement="inline"/>

</fig> <p>To create a set clock plug-in, licensees create a class that derives

from <xref href="GUID-E5ED4ACA-5EC4-3AE2-862A-AC204DCA83B5.dita"><apiname>CGPSSetClockBase</apiname></xref> and package it as an ECom DLL. </p> <p>See <xref href="GUID-F0BDE1EC-5042-5328-9290-22BB2189F6B4.dita">How to implement a LBS set

clock plug-in DLL </xref> for more information. </p> </section>

<section><title> Automatic clock synchronisation</title> <p>LBS can perform

automatic synchronisation of the system clock. LBS administration settings

configure automatic clock synchronisation. The settings define the frequency

of automatic clock synchronisation and by how much the system clock and UTC

can differ before the clock is synchronised. </p> </section>

<section><title>LBS system clock settings</title> <p><xref href="GUID-23BBC1D8-B3A0-5148-A4F1-22ECF3043E4E.dita">LBS

administration</xref> describes how to configure LBS system clock synchronisation

settings using either the LBS Administration API or a repository initialisation

file. </p> </section>

</conbody><related-links>

<link href="GUID-F0BDE1EC-5042-5328-9290-22BB2189F6B4.dita"><linktext>How to Implement

an LBS Set Clock Plug-in DLL</linktext></link>

<link href="GUID-23BBC1D8-B3A0-5148-A4F1-22ECF3043E4E.dita"><linktext>LBS Administration</linktext>

</link>