Snom ONE IP Technical Manual page 154

Deploying the snom ONE IP Telephone System
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public telephone lines (at least directly), CO-lines are still useful for determin-
ing which calls are active between the system and the outside world.
To begin with, each trunk may have several CO-lines, and because users can
subscribe to the state of CO-lines, each CO-line name must be unique within
a domain. For example, four CO-lines might be set up on trunk 1 with the
co1 co2 co3 co4 co5 co6 co7
names , while trunk 2 might contain
co8
(the list must be delimited by spaces). The system will reject names for
CO-lines that are already in use by accounts or other CO-lines in the same
domain. With regard to monitoring, the CO-lines that you establish can be
monitored from the domain's Account list. If a CO-line is in use, it will display
the extension and the outside phone number to which it is connected.
CO-Line Use
Limiting inbound and outbound traffic: CO-lines can be used to limit the
number of calls that can be assigned to a trunk. When the CO-line setting is
used, the system will reserve one line for each call. When all lines are in use, the
system will reject further calls that attempt to use the CO-line. For example, if
you have a SIP trunk that can handle only three simultaneous calls, you should
assign three CO-lines (e.g., co1 co2 co3 ). If a fourth simultaneous call at-
tempt is made, the system will play a fast busy signal. If you have more than
one trunk, you can set up a failover behavior so that the system will try to use a
different trunk for the call once the first trunk has all CO-lines in use.
Reserving lines: If you want to reserve lines exclusively for inbound traffic, put
a :i after the line name. The system will use that line only for inbound traffic
(e.g., line1:i ). If you put a :o after the line name, the system will use that
line only for outbound traffic. If there is no attribute set after the colon, the line
will be available for both inbound and outbound traffic.
Monitoring CO-lines: CO-lines are required for many basic functions. In most
small offices, transfers are done by pressing the Hold key and lighting the lamps
on the other phones. In order to do this, the phone must be able to display
which call is on which CO-line.