TELECOM Digest OnLine - Sorted: Re: What Tandem in Telcom Means?

Re: What Tandem in Telcom Means?

John McHarry (
Wed, 22 Dec 2004 03:49:19 GMT

On Tue, 21 Dec 2004 18:31:01 -0500, Jack wrote:

> I am new to telcom. I came across the term Tandem many times (eg. LEC
> Access Tandem).

> What exactly does Tandem mean?

PAT's reference is correct, but, in the meantime, a tandem office is a
telephone switching machine that stands between two end offices, the
latter serving subscriber lines. In the olden days, a couple decades
ago or less, end offices couldn't handle long distance accounting and were
connected with toll tandems that could. In very large cities there were
also, as I recall, some inter local tandems that allowed hub and spoke
arrangements of local switching.

With computer driven switches (central offices) this has pretty much
gone the way of the horse and buggy. Any office can perform most any
function required, given the appropriate software. One switch can
serve several NXX exchanges and also interface to toll carriers, or
act as part of one itself. This has also allowed routing to become
much more dynamic, adapting to changing traffic patterns.

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