Just to highlight the difference between an "RT" and a "Remote DSLAM" -- I found a USWEST/Qwest/CenturyLink installation of both a remote terminal for voice access (probably an SLC-5) and a DSLAM for data access in the same group of equipment, both connected to a single cross-connect box.

I'd noticed it a few weeks ago, and it's obvious that the newest component is at least five years old, but here's some information on it nevertheless.

First, a diagram of the local area, showing a rather interesting cross-connect box that's specifically marked as housing fiber, not very common, as well as the utility equipment, including an SLC-series remote terminal for the PSTN, and a CooledPed housing for up to four environmentally sealed DSLAMs. This is Qwest-land, so they are Adtran Total Access 1100-series DSLAMs.

Next up, some neat photos of the actual fiber cross-connect box. It is actually a few hundred feet away from the rest of this setup, but I am including it here because it's interesting, it's obviously pretty new, and I think it feeds the fiber-hole next to the CooledPed enclosure.

The labeling on the fiber box.

The actual fiber cross-connect. I think this may be the only one in town that looks quite like this. It also looks like both doors are primed to pop off, along with the bottom panels. I couldn't find any builders' marks on the actual enclosure. Maybe it's an ADH/TE product.

Now for an overview of the whole setup:

Out front is a power meter. The actual power supplies for these units is (I suspect) the box in the far back, which emits a very quiet humming noise.

Here is the label, pulled from a slightly different picture.

Here is the only labeling I could find on the power box.

Here is the power switch for the entire kit. Other than the Westinghouse label on the back here, I couldn't really find any indication of who made this box, but it appears to hinge open on both sides. I don't know if this was a DSLAM in a former life, or if this is just power equipment.

Here is the back of the SLC remote terminal. They've left some line cards on top. This unit also could use a paint job. This box is where your actual voice calls are routed.

Oh yeah I bet you want to see those line cards. Yes, I forgot to actually put the card up-side-right when I was taking a photo of it, so I just rotated the whole photo for you. They have a card edge connector on the back, looks pretty standard for the 1980s or early 1990s, maybe even older. (Think: ISA connector on your really old PC.)

Next up is the cross-connect box! This one's actually fairly unique in Qwest-land, I'd say there are maybe two or three of them in town. There are the taller boxes with “AT&T” or “Western Electric” labeling everywhere however – like you wouldn't believe. You might not, it seems like Qwest (and US-WEST before them) were extremely liberal with the application of cross-connect boxes and serving area interfaces.

If I had to make a totally wild guess, the cross-connect enclosure was made by 3M. The handle was at least.

This is the actual DSL part! On the bottom is a pretty standard cover for a fiber hand-hole. Some of them in town are labeled CenturyLink and some of them, such as this one, are labeled Qwest. My guess (which I have yet to confirm) is that the CooledPed (the beige box directly behind the fiber hole) contains up to four modern Adtran DSLAMs that are fed by gigabit Ethernet. They could be ADSL2+ or VDSL2, or there could be, say, two VDSL2 units and two ADSL2+ units. Qwest usually uses 24 or 48 port units.

Anyway what happens with these DSLAMs is that voice will come from the RT to the cross-connect box, and then from the cross-connect box to the DSLAM, and then the DSLAM muxes DSL signal and voice signal, (much like how DSL filters and Qwest DSL modems demux those signals) and then the line that has both DSL and voice on it goes back from the DSLAM out to the cross-connect box, where it further goes to the customer location.

Most cross-connect/serving area interface boxes are designed to be able to cross-connect 600 or more pairs, and this arrangement is why. Even if you only serve 192 customers off this whole setup, you're potentially making several cross-connections per customer in order to bring them voice-and-DSL service. Although Qwest/CL sells dry loop service, I haven't specifically heard anything about whether or not it's standard practice to connect voice anyway. I have a phone number for billing purposes, but when I connect a phone to my line, I don't get voice. It's likely because there are fewer voice lines available at this setup than there are DSL lines.

Oh yes, worth noting: This is not my DSLAM, but this could very well be where my voice would come from, if I had that service. The minor road this system sits next to connects with my DSLAM upstream, and I suspect this is where the T1s that feed my DSLAM are from.