Справочное Руководство для Netopia 430 s

Another use for the Optional Second Number item is for storing a 
backup number in case a connection cannot be made using the 
primar y number. For example, if calling the primar y number returns 
a busy signal, the Netopia ISDN Router will attempt to use the 
secondar y number stored in Optional Second Number. If a 
connection cannot be made using the secondar y number, the 
Netopia ISDN Router will retr y the primar y number.

If the remote network's director y number is par t of a hunt group, a 
second director y number may not be necessar y to make a 
successful connection using two B-channels.

If the B-Channel Usage item in a connection profile’s PPP/MP 
Options screen is set to Dynamic or 2 B, Pre-emptible, one or both 
B channels may be in use at any time during a call made with that 
connection profile. Use of the second B-channel depends on traffic 
volume.

In addition, one of the B-channels may be relinquished if there is an 
incoming call, or if a second outgoing connection is made using 
another connection profile.

The ability to allow incoming calls when both B-channels are in use 
depends on the type of switch protocol on the local ISDN line, and 
how that line is provisioned (configured). Some types of switch 
protocols never allow incoming calls when both B-channels are in 
use. Switch protocols that do allow incoming calls must have the 
additional call offering (ACO) parameter turned on for data. ACO for 
data is off by default.