To enable multiple device dialing
In Automatic dialing, click the Activity at least percentage and Duration at least time you want to set. Another line is dialed when connection activity reaches this level for the amount of time that you specify.
In Automatic hangup, click the Activity no more than percentage and Duration at least time you want to set. A device is disconnected when connection activity decreases to this level for at least the amount of time that you specify.
Notes
You can avoid this problem if the multilinked phonebook entry is an ISDN with two channels that have the same phone number.