Are any of the #5 Crossbar offices still in service?

The last working #5XB that I am aware of is at the Museum of Communications in Seattle, WA.

A similar working #3XB (smaller compact version of the #5XB) is at The Telephone Museum in Ellsworth, ME.

As for the public network, last time I heard of a #5XB was around 1992 or so. The last step by step switch in the US was changed to a digital switch in 1999. The last step by step switch in Canada was changed to a digital switch in 2001.

There are a handful (approximately 50 to 70) Western Electric #1AESS switches in the public network. Three in Verizon territory (one each in Baltimore, MD; Richmond, VA and Norfolk, VA), none in Qwest, and the bulk of the rest are in old BellSouth areas. I'm not sure about SBC/at&t territory, but there may be a few there.

The reason why the old step and crossbar switches are gone is primarily for Equal Access requirements. I think the FCC mandated that Equal Access had to be available nationwide by the year 2000. Hence the last handful of step switches (and XY cousins) were taken out by

1999.

Crossbar switches had rigid dial registers and routings. They tended to be the first switches to go in the mid to late 1980s. They also could not handle IDDD (International Distance Direct Dial) and couldn't handle the extra digits for Equal Access codes. The dial resgisters had a hard limit of 10 digits. Some select XB witches were upgraded as test cases, but Western Electric found it was too difficult and costly.

Independent analog switches (AE, SC, North Electric) came next (same issue as crossbar - rigid dial registers and routings - and couldn't handle SS7).

#2 and #3ESS switches couldn't be upgraded either (would have cost too much to redo the programming - cheaper to replace with a #5ESS remote).

Step by Steps came later (they normally didn't handle toll by themselves, usually routed & billed via tandem)

The #1AESS analog switches are last (since they could upgraded to handle Equal Access and SS7 signalling with an additional stand alone processor).

The first #4 crossbar toll tandem was installed in 1943, the last #4A crossbar toll tandem was installed in 1976. The first #4ESS toll tandem was installed in 1976 as well. The #4ESS replaced the #4A crossbar by the late 1980s.

The last #4ESS tandem was installed in 1999. These days, #5ESS and DMS-250 switches as well as packet switches are now being used as toll tandems. As of 2007, there are still over 140 #4ESS tandems stil in the AT&T long lines network. MCI (now Verizon Business) and Sprint LD use primarily DMS tandems, with some older DEX tandems in MCI (unless they've been replaced with DMS).

Also, the TDM (time domain) switch (5ESS, DMS-100, etc.) is approaching obsolesence. Packet switches are now being installed in some places, and we all know the dreaded four letters - VoIP. Packet switching is much more efficient, and can handle both voice and data on the same network (voice is treated like data).

So to quote a famous radio host, "... and now you know the Rest of the Story."

**************** Moderator's Note ****************

Packet switching is not new: certainly ATM, which is the best packet switching technology IMHO, is not. What _IS_ new is the public's willingness to accept gaps in calls, lat en cy, and other interuptions, and abyssmal voice quality - all the result of a generation which has grown up with cellular trans- ceivers glued to their ears.

Ma Bell did a lot of things wrnog, but they got the technical part right: any call on a Bell switch was guaranteed at least

4,000 Hz bandwidth (I exclude Mode 2 SLC, sorry). In addition, there were good standards for echo return loss, echo, etc., which made the U.S./Canada network the envy of the world.

This is the only place on the globe where people pick up a telephone and dial a number without bothering to listen for a dial tone. That's going to change, because VoIP is not a "Bell System" grade service, and it can't be made into one, no matter how hard they try.

Bill Horne

As I understand it, they are long gone from any U.S. service territory. They cannot handle SS7, which is a show stopper for starters.

Some of them were probably crated up and sent to other parts of the world where there is no money for electronic switching.

I have had Vonage since its inception. There were issues the first year, such as echo, etc. Now, it is every bit as good as any "Bell System" line.

AT$T has gotten so greedy, at least in California, that the Los Angeles Times wrote an editorial recommending that everyone who could switch to wireless or VOIP dump AT&T because of their predatory pricing.

Here is what AT&T in California now charges for everything I get with Vonage for $24.99 per month:

Line 10.69 Message Center 8.95 (activation fee $19.95) Call forwarding 5.00 (activation fee $7.50) Call waiting 5.00 (activation fee $7.50)

Caller ID 9.00 (activation fee $7.50) Three-way 5.00 (activation fee $7.50) Unlimited nation-wide calling $30.00 Unlimited calling to Canada 5.99

Total $70.63 per month.

Plus, with Vonage, I have much more sophisticated options with voice mail and call forwarding.

Also, I can have virtual numbers wherever I please. I live in Southern California and my primary number is in Washington, DC. (I have a virtual number local to my California location).

The DC number is like having a multi-thousand dollare AT$T foreign exchange line.

Sam,

I know another businessman who's had good luck with Vonage: if it works, don't fix it. My personal opinion (I'm "stepping out of the chair" here) is that the monthly cost of your Cable or DSL service must be added to the $30/month you pay Vonage in order to get the real cost: you're probably paying from $60 to $90/month for the combined total, but I hope you continue to have good luck with the Vonage service.

Of course, Vonage isn't the only player: I use the Comcast phone service, but when the $100/month "Triple Play" promotion is over, I'm going back to copper. The service has very noticeable latency and dropouts, and it lacks features that I like to have, such as the ability to turn off call waiting while on a call, and being able to erase messages before I've listened to the entire recording.

My objection to VoIP as a replacement for Virtual Circuit switching is theoretical as well as practical: there's no specification in the Internet Protocol for minimum transit time, which means that there's no way to prevent latency and other degradations caused by packet transit times without compression and queuing delays at the sending station. Even then, there's no QOS quarantee: it's just not in the protocol.

Bill

It doesn't *need* to be in the protocol; that's the beauty of it. A properly-engineered network (perhaps not the easiest thing to come by, particularly from a cableco, but they do exist) and a small playout buffer at each end (which you need anyway for echo cancellation) are all you really need.

Now I wouldn't switch my home phone service to VOIP, but that is as much because (as a network engineer myself) I need to be able to reach people even when the Internet connection is broken. But my office phone is VOIP and I've been quite happy with it. (Our campus is finally getting ready to give the heave-ho to the 5ESS when it next comes up for renewal and replace it with not one but two independent VOIP infrastructures. There's something like 12,000 lines to convert, and I'm thinking of starting a pool on when the last AT&T

7506 will leave service. Is there anyone else on Earth still using those things?)

At some point, things will get reliable enough (or I'll have enough redundant connectivity) that I'll be able to switch to VOIP at home. I wonder whether that will happen before or after Verizon itself switches to VOIP?

-GAWollman

I'm going to disagree with you on this point. A properly engineered network has to have provision for prioritization of traffic during mass-call events, which the Internet can't provide. Even in "normal" periods of traffic, there's no viable way to distinguish VoIP from data from video, etc.: at the heart of the Internet's design is the belief that traffic can be queued _at the originating end_ until bandwidth is available, and the net was never meant for real-time communications. After all, nobody cares if their email arrives at 09:00:00 or 09:00:30, but such delays are anathema to VoIP.

That's the point I hope I'm making: the Internet connection is _already_ broken as far as VoIP is concerned - there's no way to guarantee you a reliable circuit, even during an emergency.

I'm not sure an office phone system, or even a campus-wide network, is a valid model for using VoIP on the Internet. I agree that VoIP can be made to work in a controlled environment where all the factors are accounted for and planned into the system, but that's like saying that solar power will replace fossil fuels: it doesn't allow for pushback from the embedded interests whose ox is going to be gored, nor for the (often hidden) costs of updating phones and other infrastructure to connect to the new system, and especially not for the net's inability to assure bandwidth to any given customer at any given instant.

I think you're making my argument for me here: at some point, there _might_ be reliability in VoIP, but it'll need changes to IP to make it happen, and I don't see the IETF as being behind such a paradigm switch. As it stands now, the Internet is effectively an "Aloha" network, where everybody sends and then sends again if the first time didn't work. There's no capability in the net, at any point, to deliver virtual circuits - there are just a lot of under-utilized pipes that are "OK" for now, but which will fill up as more uses are found for them.

In any case, Verizon won't be switching to VoIP anytime soon: they have plenty of ATM switches to do the heavy lifting if they want to go with an all-packet network, and ATM was designed with real-time traffic in mind.

Bill

... unless you were going to pay that for an internet connection anyway (and will continue to pay for it if you switch back to POTS.)

QoS is a bit of a myth: it takes a certain minimum amount of time to get a packet (or any other signal; see Relativity) from London to Tokyo no matter what features the protocol implements. What QoS does is slow down some traffic more than others where significant congestion is encountered; as other have pointed out, the solution to this (and the only way to keep all of your customers happy, QoS or not) is to engineer a network where congestion is not a normal event. It is, on the other hand, valid to observe that packet and TDM networks degrade differently: while you may experience latency on a VoIP call, you might in stead hear a fast busy (i.e., be unable to place the call at all) on an SS7 network. It is left as an exercise for the reader to determine which is preferrable in their environment.

And my two favorite Vonage features are Do Not Disturb, and the freebie calls to Italy, UK, Spain, etc. I managed to track down a particular vintner in Spain and get a case of wine for relatively short money because of that.

And the SO has gotten info on a suit found at an estate sale by calling the UK.

It's not an apples-apples thing regarding ISP charges. For example, I get MUCH more use out of my cable net service than most people. My Vonage service runs off it as well as my Vudu service and even Joost.

A 7506? I'm familiar with the 7406D because we still use those, along with 8410D and 6408D sets.

The nice thing is that our office is wired so that we could switch the phone wiring terminations around and use VoIP throughout without the traffic riding on our main network.

We've got a Prologix G3iV11 and an older Definity G3iV6 at another location.

I need broadband for the Internet, both business and personal. Thus, as an accountant, I view the pipe is already there "for the taking" for VOIP. The accounting case becomes overwhelming when I take my Vonage adapter with me and plug it into a "free" Ethernet port at a hotel, or such.

Call waiting is even better with Vonage. I am, in effect, the "switchmeister" because I can go on-line and enter the feature and remove the feature at will. The wireline LECs should have done this years ago, but they didn't. Instead, they are making calling features a big reveue honeypot for their greedy benefit and it is going to bite them. Not so many people I know are dropping wireline for VOIP, but a lot of them are dropping wireline for wireless, at least for residential use.

The end user just doesn't care about such issues unless it affects them. I have a dedicated Vonage fax port. I recently bought a new fax machine that does 32,800 and that works just fine with Vonage. But, even the fax machine is dying out. Secured Acrobat files are a whole lot better; the limiting factor being who you can send them to.

The question of latency and other issues in the Internet will ultimately rise or fall on reasonably priced, really fast bandwidth being available like it is in other more developed countries. (that stings, doesn't it ;-) Verizon is technically going there but their pricing makes it quite unattractive.

Sam Spade wrote: [snip]

Sam,

I guess we'll have to agree to disagree on this one: I don't think that building a large pipe is appropriate when most of the time it has only a modest amount of flow: as I said, the Internet is designed around the idea of time-shifting traffic to get around bottlenecks.

At the moment, we're enjoying the surplus of bandwidth that resulted from the "dot bomb" speculation of a few years back. That bandwidth will be absorbed as other players come in and more people connect to the net, and then it'll be back to "business as usual", which is, in the case of the Internet, having to wait for your traffic to move at whatever pace the net has available at that time.

Let's remember that data links were _ananlog_ lines when the Internet was designed, and the whole idea of a packet-switched network was to obtain reliable data transfers using multiple unreliable links. It matters not that the links are now more reliable: IP just doesn't have the capability of supporting a virtual circuit, and that's what's required to have reliable telephone service.

YMMV.

Bill Horne

I was rather shocked to learn that ever since true competition came to play in RI, Verizon has lost 55% of their customers. And from what I'm hearing, not many people are signing up for their FIOS service.

RI is one of the only places where this could actually happen since the rules for network sharing are pretty one sided in favor of competition.