ZyXEL Communications ACCESSING INTERNET & INTRANET omni series - Manual (Page 80)

68 X.75 ISDN Communications
bundle request. The two data calls are established following normal
call control procedures. That is, the network treats them as two
independent calls.
The omni uses X.75 Multiple Link Protocol or 'cFos' channel
bundling protocol to coordinate the two B channels. The former
would need an overhead of two octets for each packet. The success
of bundle connection initiation is indicated by the connect message
reported to DTE as follows:
CONNECT 460800 / X.75M 128K / V42b
If a B channel is unavailable at either site then the bundle initiation
will fall back to single channel connection. In this case the connect
message may be as follows:
CONNECT 460800 / X.75 64000 / V42b
Dialing Pre-stored Phone Numbers
The 40 phone numbers stored in the NVRAM can also be used to
place a bundle call:
•
Use ATDSn, - (n=0-39), to dial the (n+1)th phone number twice
for both the bundle connections.
•
Use ATDSn+, - (n=0-38), to dial the (n+1)th phone number for
the first connection and to dial the (n+2)th phone number for the
second connection.
•
Use ATDSn+Sm, - (n=0-39; m=0-39), to dial the (n+1)th phone
number for the first connection and the (m+1)th phone number
for the second connection.
Invoking V.42bis Data Compression
The following AT commands are used to switch the V.42bis data
compression on or off for ISDN data calls when using X.75 or V.120
protocols:
•
AT&K44 - (enable V.42bis on ISDN call)