Telegraph channels today?

Anyone know what kind of "telegraph channels" are still supported today? I thought they were all obsolete and removed some years ago. (I recall seeing tariff announcements to that effect.)

In this month's Verizon phone bill, there is a notice of private line rate increases. Most items seem to be contemporary digital services, such as "DS1", "DDS", DSND, B-channel, D-packet, and VOI varieties. There are also various "analog channels" and a separate group of "voice grade channels" listed.

But there are some "Metallic Local Channel", "Metallic & Telegraph Grade Local Channel", and "Telegraph Grade Local Channel" groups. Would anyone know accurately what they are? There's a "Metallic transmission function" at 77 cents in high density areas, and $13.37 in low density areas.

I thought in telephone usage the term "metallic" refers to when they replaced single-wire--ground-return transmission with two-wire transmission 100 years ago. Also, "telegraph" meant very low bandwidth--50 to 100 baud--Baudot Teletype lines.

There's also a group called "Program Audio". Would this be high grade lines for radio station usage?

Lastly, there's a group called "Secretarial". Is this answering service?

Thanks. Public replies, please

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

"Metallic" means metal: in other words, it means a circuit using direct current signalling on copper pairs instead of one that employs tone-based or digital transmission of some sort. They were used for central-station burglar alarms, such as those provided by ADT.

Burglar alarms used to be wired in series, since they used McCulloch loops for signalling, just like municipal fire alarm boxes: each station had a different code, and when the alarm was triggered, it would break the loop in a prearranged pattern to tell the central station which node was sending. At the central station, the signal was recorded on paper tape by a register that either marked the tape with a pen or punched holes in it for each pulse: this is exactly the same way Morse designed the original telegraph system.

When I joined Ma Bell, we were taught to troubleshoot burglar alarm circuits by using a Volt-Ohm-Milliammeter at the frame, checking from one pair to the next to find an open circuit, because they were wired with _SINGLE_ wires from the ring of the first pair to the tip of the next, and so on until the last pair's ring lead would be connected back to the first pair's tip.

I always loved working on BA's: it was a sure-fire four-hour overtime, because the pairs were _never_ in the same order as the circuit card called for, and there were often additional stations that had been added or existing ones disconnected, without proper record keeping. That meant that I and a cow-orker had to "pull" the leads from each pair to the next, correct the record, test the (newly documented) pair, and then pull to the next pair.

In the early 80's, the company switched to using "burlar alarm multiples", which were just frame blocks that had been allocated for connecting the pairs in a McCulloch loop together: the back of the block was wired to provide the ring-tip, ring-tip connecitons, and ordinary pair wire was run from each cable pair to the front side. This simple innovation meant that I could find an open pair by "running the block", i.e., by just moving the tips of my pliers across the lugs so as to short each pair in turn, changing four hours of overtime into (at most) four minutes of troubleshooting. When the open pair was identified, it was only a moments time to wire a short across it until the cable was fixed.

Metallic circuits are fairly rare these days: New England Telephone dropped them years ago, ostensibly because of high maintenance costs: however, I think it was really because too many companies were using them for data circuits. A sophisticated telecom manager, faced with a choice of paying thousands per month for a T-1 line or a few dollars for a metallic "burglar alarm" circuit, would just buy some line-drivers and make his own T-1. Of course, we testmen had a lot of fun "repairing" such lines when we found them: my favorite trick was to "Box change" them from a single pair onto two defective pairs that had each had only one side open, thus providing a "metallic" circuit that was utterly useless for data. Customers who complained of noise would hear me recite a speech about the lack of a noise specification in the metallic alarm tariff.

Yeah, I know, but I was young.

ADT and other central station providers changed over to computerized alarms and modems as quickly as they could during the 80's: the new equipment provided more data (building temperature, sprinkler pressure, individual "door ajar" info, etc.), and was also _much_ more difficult for burglars to bypass. The pairs assigned to metallic McCulloch loops were converted to low-speed data, and moved from BA-multiple blocks over to two-wire audio bridges. In the few cases where metallic circuits were still provided, mostly because of "grandfathered" circuits contracted to municipalities, we would wire the local cable at each end to special T-Carrier channel units that simulated McCulloch loop operation.

Program Audio lines are for radio stations, as you surmise. As a senior testman, I did a stint on the "Radio Board": we thought nothing of spending an entire day equalizing a pair so as to attain flat frequency response from 300 to 15,000 Hz., even for a one-time remote broadcast lasting only a few hours. The tariff called for it, we delivered it, no questions asked.

I'm not familiar with Secretarial service, but I agree it's probably for TAS.

Thanks for the trip down memory lane!

Bill Horne Temporary Moderator

(Please put [Telecom] at the end of the subject line of your post, or I may never see it. Thanks!)

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when we found them: my favorite trick was

So that was you who Ernestine [called]! "Listen Buster, I'll send him over there to rip your instrument out!" ;-)

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

Well, I *was* a high school graduate ... ;-)

I should explain, before the conspiracy theorists get here, that cable pairs were in extremely short supply at the time, and because Boston had a lot of wire centers, toll cables were sometimes needed for circuits between adjacent buildings that straddled a boundary.

Sometimes we'd need a pair in a certain place, so I'd check for defective pairs in that terminal or on the toll cable that were listed as "one side open" , and if I could find two, I'd check for a burglar alarm and move it onto the "bad" pairs. The burglar alarm companies didn't care: they were _really_ using them for alarms, so continuity was all that mattered to them. But, during a six-month period, I did this twice to "burglar alarms" that were being used for high-speed data, and I had to tell the subscribers that they were getting what they had paid for, and that the pairs they used to use were now in service for someone else who was paying more.

They didn't like it, but I didn't apologize, then or now: if the tariff called for it, we provided it, no questions asked. The funny part was that that kind of a workaround became impossible when COSMOS was introduced: the computer-driven pair assignments couldn't be used if they were marked as "defective", even though only one side was open. COSMOS didn't have any code to show a pair as "Defective but usable", so the things we could do when the records were kept by hand just weren't possible when the computers took over.

I was always puzzled that the toll cables were never arranged to create Phantom, Ghost, or Wraith pairs: we certainly had enough 120C coils, but for some reason the company's policy forbade the practice and the shortage of toll cables continued well into the eighties, when T-carrier took over almost all inter-office circuits.

I used to set up "Hoot and Holler" lines between the offices by using phantoms: during slow nights when I was on "swing" shift, we'd wire up "ringdown" SF units so that the testboards could ring each other without having the boss complain about our numbers being busied out. Of course, the fact that we had a lot of vacant SF slots and extra selcal equipment was due to the fact that T-carrier _was_ taking over, so I can't protest too much.

Bill Horne Temporary Moderator

(Please put [Telecom] at the end of the subject line of your post, or I may never see it. Thanks!)

Reply to
Sam Spade

These are low bandwidth metallic lines. Just two or four wires from point to point, with DC continuity.

They are graded for bandwidth... you can get a circuit guaranteed for

16KC operation, and you can get a circuit guaranteed for 10 baud contact closure.

The radio guys get the 8KC and 16KC loops. The burglar alarm guys get the 10 baud contact closure circuits.

SOMETIMES you can get good audio bandwidth across an alarm circuit, but it's not guaranteed. It sure is cheap, though. Likewise I have run T-1 circuits over 48F leased lines for five bucks a month... but it is not guaranteed.

Today it means there is physical copper from one end of the line to the other. The circuit is balanced, but it's not being multiplexed over any sort of trunk circuit.

Yes, precisely. There are still plenty of remote sensing applications where low bandwidth signals and DC circuits are needed.

Yes, that is where the 16KC and 8KC radio loops would be. IF you can get them today, which is rapidly becoming an issue.



--scott -- "C'est un Nagra. C'est suisse, et tres, tres precis."

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

IIRC, D-4 banks can be equipped with 5 KHz and 8 KHz program audio cards: they work by using multiple timeslots. I don't think D-4 can be used for 15 KHz, but it's been awhile.

Broadcast stations have other options now: remote pickup transmitter/receiver setups, adapters that allow program audio on ISDN or multiple POTS lines, and satellite.

Bill Horne Temporary Moderator

(Please put [Telecom] at the end of the subject line of your post, or I may never see it. Thanks!)

Reply to
Scott Dorsey

Yes. A secretarial line is one which is 3rd legged to an answering service. Its pretty much a thing of the past but a few are still out there. In the days before call forwarding, secretarial lines were the only way to get your phone answered off site.

- Ron

Reply to
Ron Kritzman

That was a very common business service arrangement, even if the phones were in different exchanges. I knew of many small stores that had two locations where the phones rang for both. Of course, there were charges for this feature. For some reason, it was/is available only to business customers. Residential customers may get it on a temporary basis only.

A friend has two properties, both within a single exchange. He'd like the same number at both so he could answer his phone at either location. It would seem easy to provide, just parallel the lines from the two properties to the C.O. It was explained by a poster that providing that service isn't that simple, that some sort of balancing is needed. For residential customers they'll do it for a few months (say for someone who is moving), but that's it.

I was told another use of 'metallic circuit' was for "lift handset" phone service, which is still in use in some places. That is, a person in a remote spot merely lifts a handset and a phone will ring elsewhere to assist. It may not be cost effective today as in the past. As mentioned elsewhere, some new train stations have pay phones, subsidized by the carrier, to serve mostly as an emergency 911 phone as opposed as a public convenience. I don't know what the monthly subsidy cost to provide a pay phone that won't make money on its own, but wouldn't be the basic line charge and maybe a rental for the pay phone set itself? Would anyone know accurately what the cost is?

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

It's called an "Extension Off Premise", and it's billed by mileage. "Some sort of balancing" _may_ be needed, but is usually not required: a simple "Bridge Lifter" would isolate the leg that wasn't in use on any given call. Most people who apply for it are upsold a package that includes call-forward-no-answer to a separate number, but some businessmen insist on getting the first ring at both locations and are willing to pay the freight.

I don't think there's any "Lift Handset" service: you may be thinking of Manual Service, which is used by impaired customers who can't dial a call themselves. The only arrangements I've seen are semi-automatic phones that dial Zero when a activated by button, blow tube, etc.: the caller is connecte to the operator and gives the number verbally.

There are still Private Line Automatic Ringdown (PLAR) circuits available, and they ring the other end when someone lifts the handset, but they're also billed by mileage, and they're mostly used by taxicabs that want to lasoo business from supermarkets or train stations. Ma Bell's focus has been on shared trunking for _all_ services for some years now, and private lines are getting harder and harder to obtain.

Bill Horne Temporary Moderator

(Please put [Telecom] at the end of the subject line of your post, or I may never see it. Thanks!)

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WECo Channel units for D4 Channel Banks supported three types of PG (Program Grade) audio services. 5Khz, 7.5/8Khz, and 15Khz. 3Khz lines were provisioned using TO4 channel units that were wired based on the A to Z circuit configuration. Coastcom also produced PG channel units for D4.

As the market for D4 PG audio channel units began to dry up in the early

1990's, Pure Digital end to end systems replaced the hard to find D4 PG channel units. The newer digital systems employed proprietary HDSL over a single wire pair to a HDSL remote audio unit that is capable of supporting up to 768Kb/s. Equal to twelve DS0 channels.

The 768Kb/s provided capacity for two 15Kh/z audio channels in a stereo L-R configuration over a single wire pair. The PG system used by NYNEX, latter Bell Atlantic-North, employed equipment from XEL Communications. The XEL system was compatible with the WECo & Coastcom 15Khz units when used at the far end D4 bank of the T1 system.

I was on the Transmission Engineering staff at NY Telephone who evaluated the XEL equipment, as well as other D4 based FT1 equipment in


Boardcasters were not too fond of the XEL digital units, since one of the main complaints was the lack of audio headroom on digital equipment, along with quantizing noise/distortion. Radio ststions transmitting classical music were the most critical of the XEL units.

In 2001 I specified funtional requirements, then performed test & acceptance for deployment in Verizon East (fBA region) of a replacement for the D4 XEL HDSL units. The replacement comprised an Adtran ISDN channel unit (UBR1TE-V), and a station package manufactured by Pulsecom known as the Program Channel Audio Unit (PCAU).

Using the PCAU, and a UBR1TE-V (With the D Channel turned off, DDS mode), a 7.5 or 15Khz program audio channel can be transported across a T1 line using one or two DS0 chanels. The PCAU employs a patented compression scheme that permits up a 7.5Khz audio channel to be carried over a single DS0 B channel, and two DS0 B channels to carry a 15Khz line.

A PCAU is required at each end of a PG audio channel. WECo/Coastcom and XEL PG equipment are not compatible with the PCAU/UBR1TE-V circuit combination.

The ISDL/PCAU circuit design allows for the first time provisioning of PG audio channels over digital loop carrier systems using native ISDN channel unit equipment. A capability that was not possible, except on SLC-96 systems.

I hold the US Patent, assigned to Vz, that permits a UBR1TE ISDN channel unit to respond to in-band DDS loop codes (When the D channel is disabled on the D4/SLC-5 channel unit), and when used in conjunction with an Adtran OCU-R at the customer location. The IDSL design will deliver traditional 4W DDS services over a 2W IDSL loop.

During the development of the Adtran channel unit, I required the manufacturer incorporate additional features to support loopback capabilities not typically used in the DDS-IDSL application. Such as remapping in-band DDS latching CSU loopback (Along with DS0-DP loopbacks), over the ISDN's embedded eoc channel as a NT1 loopback message.

The idea was to permit a digital leased line service capable of up to

128Kb/s to be introduced using a U interface at the customer location that terminated into either an ISDN/ISDL capable router interface (WIC), or ISDL (non-switched ISDN) data communications equipment.

The PCAU was designed to respond to a NT1 loopback over the IDSL eoc, similar to an end office switch performing NT1 BER test on an ISDN-BRI loop. The PCAU also incorporates a V.54 in-band loopback to further help maintenance personnel sectionalize circuit troubles over the metallic or DLC loop(s).

Testing the T1 portion of the audio channel is performed by operating a remote loopback at the UBR1TE-V via an in-band DDS DS0-DP latching loopback. On tandem BR1TE cad connections, such as on back to back channel bank designs, use of DS0-DP loop codes follows conventonal DDS testing strategy.

For test center personnel, the learning curve involved with PG audio testing is not as difficult to adopt when compared to previous methods.

The first application of a PCAU/UBR1TE-V circuit design was at a New York classical radio station in 2002. Two circuits were ordered by the station to evaluate the new equipment. One circuit was used on a remote studio audio broadcast link used during newscasts, and the second circuit as a talk-back audio feed for the broadcast news link. Both circuits were provisioned for 15Khz.

Since the initial introduction of the 7.5/15Khz PCAU in 2002, Pulsecom has introduced a HD PCAU capable of supporting 20Khz audio. Unfortunatly I am not intimate with the newer HD PCAU since I am no longer with Vz, however based on information from Pulsecom's web site, the HD version appears compatible with the original IDSL transport equipment I performed development work on.


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

Thanks for your post, Bill: that fills in a big gap in my understanding. Since D-4 banks were "sorta" MD'd years ago, I'm curious if any of our readers know whether the IBOC's are still getting them from second-source suppliers, or if they've been replaced.

Bill Horne Temporary Moderator

(Please put [Telecom] at the end of the subject line of your post, or I may never see it. Thanks!)

Reply to

I suspect the service told to me was a "PLAR" circuit.

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That would (assuming "New York" refers to the city) presumably be WQXR, during the period when their newsroom was located in the /Times/ newsroom, in the old /Times/ facility, but the air studios were elsewhere.

Most NYC stations use microwave (to the extent frequencies are available) and telco T1 circuits for studio-transmitter links. Normally the stations will do their own multiplexing on the T1 using a Harris Interplex or similar products; this allows them to run digital end-to-end, and to provide private-network IP connectivity at their transmitter sites, which is becoming a necessity these days.

I suspect a few of them still have old copper program lines which they keep as a backup-backup. (The radio engineers I know seem to spend an inordinate amount of time dealing with telco issues.)


Reply to
Garrett Wollman


I've installed several of these IDSL Program Audio Broadcast loops using the PCAU cards and can indeed attest to their robustness. Thanks for helping to provide a quality product/service for us techs in the field.

The PCAU is a huge step forward in Broadcast Loop technology. First, it's easy for the installer to install. All you need is a good, clean and balanced *unloaded* cable pair. Second, the PCAU board and a suitable housing. I've found that 2 or 4 slot T-1 housing work perfectly when coupled with the optional 48v power supply. I've found that the older single slot stand alone analog mountings won't work as the internal 48v power supply doesn't appear to have enough current capacity to power the PCAU. Also a 4 slot T-1 housing will nicely accommodate two PCAU's for stereo applications. The PCAU uses 400 style mechanics which are twice as wide as the mechanics for T-1 smartjacks but the pinout of the cards match allowing the use of a card in slot 1 (hangs over slot 2) and a second card in slot 3 (hangs over slot 4)

Since the PCAU is digital end-to-end and the digital data stream is encrypted, there is no place to "get in the middle" of the circuit and monitor the audio. This is a "good thing" as far as security is concerned but a "bad thing" as far as circuit testing is concerned. Testers can only do loopbacks to the PCAUs but can't always determine where the real trouble lies without dispatching to both ends.

Also, many testers don't even know the correct way to test these beasts. I can't tell you how many times I've had to tell a tester that they

*can't* bring up an audio monitor test point, that the only test point is at the digital level and they need to test this like it was a DDS circuit. They then get totally confused. 8-(

The one really good thing about these units is that they either work or they don't. There is no level adjusting, no equalization to adjust or much else. Plug it in and see if you can get a signal from "A" to "Z". If you can then the levels will be good and the slope will be nearly razor flat.

I guess you can tell I like them. 8-)

I keep a spare PCAU plugin on the truck, just in case of trouble.


Reply to
John P. Dearing

"John P. Dearing" wrote in news:DSVKj.19517$Ah1.998@trnddc08:


Unfortunately you are correct from the SSC tester's point of view. There is no capability to put a PG Audio circuit into monitor using REACT, as done with typical analog DS0 circuits.

The same was true when using conventional WECo D4 PG Audio plugs, and the XEL Program unit that was strictly deployed in the former NYNEX region of Vz. Remote test systems do not have the ability to drop multiple DS0 channels that make up the PG channel.

However I have been able to drop out PG Audio channels during hard troubles by using a few unorthodox methods that a typical Technician does not do. For example, a conventional 15Khz PG audio channel can be monitored (Dropped) in the middle of a T1 span mid span by first using a T-Berd test set plugged into a DSX-1 MON jack, then taking the output of the monitored signal from the T-Berd, which now acts as a T1 Span repeater, and plugging it into the DSX-1 IN jack of a spare D4 channel bank equipped with a 15Khz Receive unit.

I have done this many times for many types of troubles, typically DDS, when I have had drop out DS0 signal from an active T1 CXR span.

You are correct about the -48VDC current requirement. At the WQXR installation the SS tech used a single 1.25ma Westell (Black) power supply to power two PCAU's. The Westell power supply over heated, and then shut down. It would then turn on again when cooled, and then shut down once again repeatedly. I was surprised that the Westell did not fail completely. I once found one wired to power two Teltremd 5760 T1 NIU's in a double slot mounting. The DC supply did not pass the smell test.

I had the single 125ma Westell unit replaced by two Teltrend 250ma supplies. I know that at the time Teltrend made a single slot 200/400 type mounting with a built in DC power supply capable of powering one PCAU. But if you use the old Teltrend, now Westell, An onl Teltrend, now Westell, Four Pack mounting used on T1 & DDS circuits makes a good 15Khz PG stereo circuit termination package that includes a 500ma -48VDC power supply.

When Pulsecom approached us back in 2000 - 2001 to evaluate the PCAU, I saw an opportunity to build in as many test maintenance features as possible. The developer at Pulsecom, I heard back in 2003 that he no longer was working at Pulsecom, was very helpful with what we (Vz) were looking for in the unit, plus PG channel performance.

At the time of development Pulsecom was also asked to allow wire only operation between two PCAU's with no D4 channel bank in the design layout (Campus House loop). Two PCAU's will operate over a non-loaded copper loop of up to 40dB insertion loss at 40Khz (ISDN/ISDL Nyquist). This is accomplished when one PCAU clock option is set to MASTER, and the other to SLAVE. Pulsecom's equipment practice describes this capability.

I was fortunate to have written the technical & operational specifications to the BA 2W DDS RFP in 2000, so I was intimately aware of the capabilities of the D4 UBR1TE-V channel unit. Enough test maintenance & PM data collection capability was built into the IDSL & Total Reach DDS units, that a field technician equipped with the proper test tools can diagnose, and clear a loop or local equipment trouble before even calling a test center.

Lessons learned from an intermittent AT&T DDS access line trouble using the a conventional 4W loop out of the Richmond Hill CO in Queens back in

1998. That trouble took about four months+ to resolve a combination of CPE I/W, plus an intermittent swinging open in the F2. During this trouble I experimented with a modified Teltrend ISDN channel unit in the local D4 bank, and a remote Teltrend IDSL DDS beta unit similar to the Adtran IDSL OCU-R of today.

At the time I was also fortunate to have had access to DDS channel monitoring data at the AT&T test center chronic group located at Richmond, VA, since AT&T DATEC had been looking at this trouble before BA was called. It didn't hurt that a long time friend was working this trouble at DATEC, hence the chronics group data. We both had once worked as AT&T overseas operators back in the early 70's.

If the present line up of 2W DDS equipment w/PM was available back then, the troubles would have been identified in less than two weeks.

It sad at how much the technical support groups have been reduced in size, and scope of how they do their work today. In today's environment, I would no have had the ability to spend the amount of time I did on the Richmond Hill trouble. Yet in the end, that trouble helped identify a requirement for an improved method to trouble shoot DDS circuits. Which up until a few years ago, was a much slower, frustrating and intensive process.

I can send you the Adtran 2W DDS Power Point training package if you like. It will reveal many of the then "new" maintenance features that only, to my knowledge, Verizon has incorporated. A source at Adtran used the term "Cadillac" to describe BA's 2W DDS equipment features back in




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