In the case of OpenScape 4000 with a cPCI controller, the front reference can continue to be connected to the MCM module and the "external clock box" connector with the special frontref cable (S30267 – Z319 – A150). It is distributed to both clock generators on the RTM module. Configuration with the AMO REFTA remains unchanged.

The front reference in every IPDA can also be used. If the cordless coverage areas of several nodes overlap, (e.g. of several IPDAs), these nodes must be synchronized with ISS in order to avoid dropped call in the overlapping area and to enable switching nodes during a call. All base stations in a continuous coverage area of a cordless system must be synchronized according to the DECT requirements to enable a seamless handover, regardless of whether they are connected to a IP access point (AP 3300 IP, AP 3700 IP) or a host system frame (AP 3300, AP 3700). To do this the IP access points must receive synchronization signals from a GPS receiver. The AP3x00 IP IP access points with the NCUI4 control board enable the handover between base stations connected to two IP access points.

To date the ISPA requires a TDM line as a base clock and the GPS clock for advanced settings for ISS. By using the front reference, the TDM line does not need to be used as a clock supplier. The clock is now provided solely from the GPS receiver. The GPS receiver clocks once via the NCUI front reference input and SLC24 clocks via the SLCSS board.

A cluster of several IPDAs at one site can be supplied to by the clock distributor via a GPS receiver.

The GPS signal ensures the GPS receivers are synchronized and therefore also that the IPDAs or the IPDA clusters are synchronized. If an IPDA cluster has no overlapping area to a cluster clocked by another GPS receiver or separate IPDA, this cluster can operate without a GPS signal. This means that the receiver generates a dummy signal to synchronize in a cluster but does not require a GPS antenna.

The AMO REFTA can be used to configure and prioritize the frontref separately for every IPDA.

The frontref that can be used to operate OpenScape 4000 satisfies the UTI G.703 § 13 recommendation with wave resistance of 120 ohms.

ADD-REFTA:TYPE=FRONT,PRI=89,LTU=17;
 
CHANGE-REFTA:TYPE=FRONT,PRI=90,LTU=17;
 
DELETE-REFTA:TYPE=FRONT,LTU=17;