How Many Additional Devices
Additional devices such as fax machines, PCs, pay-phones, video conferencing terminals and burglar alarm lines have historically been connected outside the company's telephone system with a dedicated line for each device. The cost of these lines is some £150 per year each.
The good news is that these devices do not need a dedicated telephone line anymore. 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 that these devices can share lines (channels) from the main system, therefore saving a substantial amount of money. But they still can have a dedicated 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 for different marketing campaigns would allow you to monitor the response from these campaigns, without investing in separate telephone lines.