D.1.3 Operation of several SX2 cards in one computer
It is possible to operate several ISDN cards in one computer. On performance grounds, we recommend operating a maximum of 76 ISDN channels from one computer. Combinations of different SX2 cards are also possible; a maximum of four logical cards, for example:
*four SX2 QuadBRI
*two SX2 DualPRI (one SX2 DualPRI is equivalent to two "logical" cards)
*two SX2 SinglePRI and two SX2 QuadBRI
*one SX2 DualPRI and two SX2 QuadBRI
Synchronizing the SX2 cards
If there are several SX2 cards in one computer, three cases can be differentiated:
*All cards are directly connected to the public line (TE mode)
In this case all cards receive the same pulse from the public line. There is no need to synchronize the cards.
*All cards operate internal lines (NT mode)
If all cards are operated in NT mode, synchronization is recommended if a call is made via two different ISDN cards.
*Mixed operation of cards in TE mode and in NT mode
If a call which is e.g. coming via an ISDN card from the public ISDN, is forwarded via a second card in NT mode e.g to a sub-PBX, the two cards should be synchronized. That is, the card in NT mode gets its pulse from the card that is connected to the public line.
 
For synchronizing two SX2 cards, you need a special cable: "Synchronisation Cable EXSG 10002".
 
This is how you synchronize two SX2 cards
1 The two cards must be connected to each other with the Synchronisation Cable EXSG 10002.
The SX2 cards are in front of you with the PCI plug strip facing down and the ISDN connections to the left. Regardless of the type of ISDN card, you will then find two PCM plug strips in the upper right corner. The upper plug strip is labeled "OUT", the lower one "IN".
Fig. D-1: Schematic representation of SX2 SinglePRI
2 Now connect the "OUT" plug strip of the card that will be operated in TE mode (master), to the "IN" plug strip of the card that is to be operated in NT mode.
3 Insert these connected cards into the computer (15.2.5 Insertion of the ISDN Card).
4 If no driver has been installed for the SX2 cards, it can be installed after this insertion (15.2.5 Insertion of the ISDN Card).
5 Next, start the configuration of the driver in computer management (15.2.7 Configuration of the ISDN Card).
Enter the appropriate settings under "Properties".
6 Select "ISDN Parameters" on the "Advanced" tab.
7 In the tree structure, highlight the ISDN controller of the card that will be operated in NT mode.
For details of how to identify the ISDN controller, please refer to The "ISDN Ports" Tab.
In the information field "Connected to:", it should now be indicated that a PCM cable has been connected to the card.
In the field "Clock source for lines in NT mode", activate the option "Obtain clocking from other board connected via PCM bus".
8 In the tree structure, highlight the ISDN controller of the card that will be operated in TE mode (master).
Here, the option "Derive clock from line in TE-mode or use on-board clock generation" must be activated in the field "Clock source for lines in NT mode".
 
If you want to operate multiple cards in NT mode and synchronize them with a card that is connected to the public line in TE mode, you can feed through the pulse from the public line with further synchronization cables. To do this, connect the "OUT" plug strip of a previously synchronized card (NT mode) to the "IN" plug strip of a further card in NT mode, and so on.