This feature is available only in the USA and Canada.

The calls are usually passed down or 'rolled over' to the next available telephone line in a preset order.

Your machine can work in a rollover system only if it is the last number in the sequence, so the call cannot roll away. Do not place the machine on any of the other numbers; when the other lines are busy and a second fax call is received, the fax call would be transferred to a line that does not have a fax machine. Your machine will work best on a dedicated line.