» cFos for X.31

cFos X.31

Configuring cFos for X.31

First, set the D-channel (Case A):

X.31 is the protocol used for data transfer through the ISDN D-channel. If you wish to activate this service, you will first have to request what is called a "TEI" from your phone carrier. For more information on getting X.31, consult your provider (for instance, German Telekom customer information can be reached at 0130-801180).
You will also need an X.31-compatible ISDN board with CAPI 2.0 (capi2032.dll) (e.g., by AVM, Bintec, Diehl, HST, ITK, or NCP). cFos supports X.31 for CAPI version 2.0 and higher. It allows management of several TEIs on different COM ports and/or several logical channels on a single TEI and different COM ports.

Basic Settings:

Use modem command " ATB13 " to configure protocol settings as needed. The following registers will then have to be set before X.31 can be activated:

S23 = t
TEI setting: t = TEI * 2 + 1
S45 = n
n = 0: no delivery confirmation
n = 1: delivery confirmation (only CAPI 2.0)
&S3 = <data>
Call User Data, coded by hex digits with a maximum of 32 octets.
For example, by setting " AT&S3=414243 ," you can code the Call User Data 'ABC', as the hex number code for A, B, and C is 'A'=41, 'B'=42,'C'=43; so you get 'ABC'=414243.

" ATS10.14=1 " activates X.25 more-data support. This means that cFos will send data blocks with a 'more-data' bit as long as there is still more data remaining in the buffer at the time of transmission.

Logical Channel Settings:

Default is one bidirectional channel (which is assigned No. 1). This setup should work for approximately nine out of every 10 applications.
Should you need different settings, however, follow these steps:

First, enter the highest and the lowest bidirectional channel numbers (given to you by your ISDN provider) in S32 and S33. Then enter the lowest channel number for incoming calls in S30 and the highest in S31. Set lowest and highest channel numbers accordingly for outgoing calls in S34 and S35. If no specific values are entered for one channel type, all respective registers will automatically be set to '0.'

Example 1:
Setting channels 1 and 2 for incoming and outgoing calls would look like this:
" ATS30=0 S31=0 S32=1 S33=2 S34=0 S35=0 "
Example 2:
You want to use channels 1 through 6 – 1 and 2 for incoming calls only, 3 and 4 for bidirectional calls, 5 and 6 for outgoing calls. Settings for S30 through S35 would have to be:
" ATS30=1 S31=2 S32=3 S33=4 S34=5 S35=6 "


If you want to use PVCs, S46 has to be set as follows (CAPI 2.0 only):
S46L = Group number
S46H = Logical channel number

Activation and Connection:

First, save the settings described above in the modem profiles (e.g., by using " AT&W1 "). That way, you can restore them later by using " ATZ1 ".

After using " ATZ1 " activate the connection to the packet handler via " AT&X1 ". If you want to modify settings later on, you will have to deactivate this connection by using " AT&X0 " before making any changes.

After activation by " AT&X1 ," you can use " ATD<number> " to set up a logical connection (for PVCs, you are free to pick any number you like).

As for any dial-in connection, Windows DTR drop is used to disconnect.

With register S74.8 set, the connection will also be closed in case of inactivity.

X.31 in the B-channel (Case B):

You will have to initialize the connection with " AT&F B13 " as described above. Then, logical channel numbers need to be configured.
However, a TEI needs not be specified, as S23 is used as X.75 link address A.

Now, the caller ID of the packet handlers has to be set using " AT&S11=xxx ."

After that, set " AT&X1 " instead of " AT&X2 " to establish a connection to the packet handler. HDLC/X.75 is used as B-channel protocol.
Connecting (to a logical address) is done exactly as for the D-channel (by using " ATD... ").

Note: The B-channel connection established by " AT&X2 " is subject to charges and should be deactivated by " AT&X0 " at the end of each logical connection!

To use Remote Configuration and X.31 together, cFos needs to be loaded on at least two ports.

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