TELECOM Digest OnLine - Sorted: Re: Physically Protecting The Local Loop Metwork?

Re: Physically Protecting The Local Loop Metwork?

Al Gillis (
Sun, 25 Dec 2005 18:29:54 -0800

Gordon Burditt <> wrote in message

(Snip, ship, snip...)

> A long time ago, when they first started allowing other people to
> connect modems to a phone line, but NOT directly, there was the DAA
> ("Data Access Arrangement", I think). I worked with these in the late
> 1970's. You rented it from the phone company. It had a defined
> interface so you could pass voice through it, take the phone off the
> hook, pulse dial, detect ringing, etc. For tone dialing you'd just...

(More Snippage...

There was also a gizmo of much the same circuitry called a VCA --
Voice Connecting Arrangement. A VCA was used on a trunk connecting a
common carrier's service to a customer owned PBX. While a stand alone
VCA was pretty simple, when there were a lot of them there was a lot
of stuff - equipment racks, mounting shelves, distributing frames, and
who knows what other manner of monkey business. At least there was no
power - as I recall these VCAs (made by TelLabs) used no external
power. (A "DanRay" PBX I installed in the early '80s had nearly 300
trunks and an equal number of VCAs! These were installed in a room
separate from the PBX and consumed quite a footprint).


(Oh -- Merry Christmas and Happy New Year! Thanks for helping to educate me
throughout all of 2005 -- and several years before that as well!)

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