Additional
devices such as fax machines, Pc's, pay-phones, video conferencing
terminals and burglar alarm lines have historically been connected
outside of a companies telephone system with a dedicated line
for each device.
These devices do not need a dedicated telephone line (costing
some £150 per year each), they need a dedicated telephone
number. Using ISDN
lines you can have many telephone numbers even if you are
only having a few lines (or channels in ISDN
speak). This means these devices can share lines (channels)
from the main system, therefore saving a few £150's.
But they still have their own telephone number.
This set-up will also have other advantages such as the ability
to easily analyse calls to and from these devices. Using two
numbers from your DDI
range on say one fax machine would allow you to monitor the
fax-back response from a marketing campaign separately from
your day-to-day faxes, without investing in a separate fax
machine and telephone line.