TELECOM Digest OnLine - Sorted: Re: Typical Business Telephone Sets Today?

Re: Typical Business Telephone Sets Today?

T. Sean Weintz (
Thu, 04 Aug 2005 11:40:30 -0400 wrote:

> My department at my employer uses plain 2500 style telephone sets
> under a Centrex system. I kind of assumed they were still common
> place, but I understand now that they're kind of unusual? I heard
> caller-ID is very common on business phones, is that true?

Every office I have ever worked in has had a PBX system using some
sort of proprietary keysets.

Every office I have ever worked in since '95 has had keysets with an
LCD display that (amomg other things) displays caller ID.

Centrex is a ripoff IMO. Especially for offices where most of the
calling is in-house. Why pay for a line for each station when say only
20% of your calls ever go outside the building?

[TELECOM Digest Editor's Note: Even in the case of Centrex it is very
rare that telco provides an _actual wire pair to the outside_ for
every phone thus equipped. Using Erlang or other formulas, they decide
a ten or fifteen percent ratio of wire pairs to usage at any given
time is sufficient. When calls come in from outside, something like
ANI examines the number dialed, chooses an idle pair and rings the
desired extension. On outgoing calls (even on centrex you still have
to dial '9' first) the equipment looks at the outgoing line, uses its
ID number to detirmine what caller ID to send to the called party,
etc. If a centrex user ever dials '9' for an outside line and gets
a fast busy response, it means one of two things: either the phone
in question is not given outside dialing privileges _or_ the limited
number of trunk lines is totally in use. And with centrex, your call
(inside or outside the customer premises) is still taken to the
telco central office for processing, even if the end result is the
call is, following processing, sent right back inside your premises
as a 'station to station call'. Remember that 'centrex' means that
telco has your 'PBX' on its premises rather than in your office.
Otherwise calls in or out are handled about the same way and with the
same rules in place. PAT]

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