241
6620-3201
8 Using V.120
V.120 is a protocol designed to provide high-speed point-to-point communication over ISDN. It
provides rate adaptation and can optionally provide error control. Both the calling and called units
must be con
fi
gured to use V.120 before data can be transferred. Similarly, if one unit is con
fi
gured to
use the error control facility, the other must be con
fi
gured in the same way.
8.1 Initial Set Up
Before using V.120 you must
fi
rst bind one of the two available V.120 instances to the required ASY
port using the
Confi gure
>
Protocol Bindings
page or by using the
bind
command from the
command line, for example:
bind v120 0 asy 0
You should also select the appropriate method of
fl
ow control for the ASY port using the
Confi gure
>
ASY ports
page or by using the AT&K command from the command line. Other ASY port options
such as command echo, result code format, etc. should also be con
fi
gured as necessary.
8.2 Initiating a V.120 Call
Once the initial con
fi
guration is complete, V.120 calls may be initiated using the appropriate ATD
command. For example:
atd01234567890
A successful connection will be indicated by a CONNECT result code being issued to the ASY port
and the unit will switch into on-line mode. In this mode, all data from the terminal attached to the
bound ASY port will be passed transparently through the unit across the ISDN network to the remote
system. Similarly, all data from the remote system will be passed directly to the terminal attached to
the bound ASY port.
If a V.120 call fails the unit will issue the NO ANSWER or NO CARRIER result code to the ASY port
and remain in command mode.
The ATD command may also be used to route a call to an ISDN sub-address by following the
telephone number with the letter S and the required sub-address value.
For example:
atd01234567890s003
In this case, the remote system will only answer the call if it has been con
fi
gured to accept incoming
calls on the speci
fi
ed sub-address.
