Advantages of ISDN
1. DDI The ability to have multiple telephone numbers even with a small number of lines (or channels in " ISDN speak"). This allows for fax machines, PDQ's, private lines, alarms systems etc. It also facilitates the ability to answer the phone in different company names and analyse the response to advertising. This just scratches the surface of the available functions.
2. CLI The ability to see who is calling you before answering the phone. Also it keeps the telephone numbers of historic callers, so no more lost customers through messages taken with incorrect telephone numbers. Calls can be automatically routed directly to the relevant department, such as straight to accounts or marketing.
3. Video conferencing. Again not yet perfect but useable over ISDN.
4. Trunk to trunk transfer. Calls can be transferred directly from your office to any other number in the world. For example to your mobile, home or even your holiday villa.
5. In today's high-tech age it is not financially sound to purchase new equipment that is not at least close to the leading edge. Whatever high-tech equipment is purchased today (telephones, computers, fax machines, video's, hi-fi's etc) is out of date in a very short space of time.
The best advice we can give at Phones4Less regarding any technology is, think of the technology industry as similar to comparing the age of your dog to the age of a person, i.e multiply by 7. If an item of hi-tech is 3 years old it is the same as a low-tech item being 21 years old
A full Non Technical explanation of what ISDN can do for you, from a voice (not data) point of view can be found by following this link ISDN In English.