Category Archives: History

The Anti-Digit Dialing League

In 1962 Pacific Telephone and Telegraph announced that it would remove exchange names,

Up until this point in the US telephone numbers had been prefixed with the exchange name, as a one or two letter code, which would be used in place of the digits when you dialed,

For example if you were on the GArfield exchange (GA) you’d give your number as GA 1234 or GArfield 1234, to dial this the GA would just be converted into numbers based on the dial, so GA = 42 1234.

The Bell system had wanted to do away with this for a long time – it’s inflexibility meant digits that spelled out the prefix of common place names were filled up, while others were almost unused, and was not conducive to the growth patterns of telephone systems. Letters alone limited the dialing plan to 540 combinations for the area code, for 186 million Americans at the time, while moving to all-numbers opened up for use the 0 and 1 positions on the dial (which don’t have letters associated with them), expanding the pool.

The North American Numbering Plan (NANP) had been divided by AT&T in the 1940s and from 1951 onwards was being rolled out across the bell system, so it shouldn’t have come as any great surprise that in May of 1962 Pacific Telephone and Telegraph, like many other Bell system companies, made the announcement instead of exchange names, there would be a 3 digit exchange code / area code, followed by 4 more digits for the local subscriber, what it called “All-number dialing”.

This is where our story would end if it weren’t for some outcry of locals regarding the loss of their beloved exchange codes. Letters to the editor of local newspapers led to polling by the San Francisco Chronicle revealing two-thirds of their readers opposed to all-number dialing, which led to one man – Carl V May, taking out an advertisement in the the local newspapers with a simple one line statement and address,

Join the Anti-Digit Dialing League

P.O. Box 996, Sausalito, Calif

The ad received over 3,500 responses, and a sizable following for the group sprang up practically overnight, united in their opposition to the loss of the exchange letters and the “creeping numeralism” being pushed upon them.

These people are systematically trying to destroy the use of memory. They tell you to ‘write it down,’ not memorize it. Try writing a telephone number down in a dark booth while groping for a pencil, searching in an obsolete phone book and gasping for breath. And all this in the name of efficiency ! Engineers have a terrible intellectual weakness. ‘If it fits the machine,’ they say, ‘then it ought to fit people.’ This is something that bothers me very much: absentmindedness about people.

S. I. Hayakawa

To be clear, automation and the removal of switchboard operators for local calls (Direct Digit Dialing (DDD)) (“Subscriber Trunk Dialing” or “STD” as it’s known in the UK and Australia) had happened already, so this wasn’t about people losing their jobs, but rather Citizens wanting to keep the letters of the places their dialing.
Nor were phone numbers themselves changing due to All-Digit-Dialing, if your number was GA 1234 you’d still dial 42 1234 to get there, it would just be printed as 42 1234 instead of GA 1234 in the phone books.

A steady stream of telephone customers–“mainly from the Valley,” said a Times account of the local hearings–complained that ANC was dehumanizing, violated tradition, eliminated a sense of community, increased dialing errors, made phone numbers more difficult to remember and ran up phone bills, because people no longer knew where they were calling.

ADDL’s support continued to grow, badges appeared and a legal challenge was mounted against the phone company to prevent this, and a restraining order was issued to halt the project, and the Public Utilities Commission had to go through 3,200 pages of testimony from hearings in Los Angeles and San Francisco on the impact of the All-Number-Calling system.

The 25 cent lapel pin available for members of the ADDL

Comedian Alan Sherman wrote a song called “The Let’s All Call Up A.T & T And Protest To The President March” on his 1963 album “My Son, The Celebrity”, which hasn’t aged well…

But progress marched on, the restraining order was quashed and by 1964 NANP rolled on, and all-digit dialing continued to be rolled out across the rest of North America.

And as quickly as it appeared, the ADDL was gone.

NANP continued and phone numbers were changed and expanded several times since then, but never with resistance as strong as that of the ADDL.

While researching this it reminded me of Reply All episode #104 The Case of the Phantom Caller.

Further Reading

The Farmville herald., January 04, 1963, Page 1B, Image 9

The Chronicle., August 28, 1963, Page ELEVEN, Image 11

The Day of the Digits: Postscript to the Prefix War

How AT&T tried (and failed) at mmWave Deployments the 1960s before 5G

So this is the story of how in the 1960s AT&T’s Bell Labs bet on millimeter waves being the communications medium of the future, 60 years before 5G’s millimeter wave hype.

While it’s technically autumn, I just finished my summer Telco reading list, which included “The Idea Factory: Bell Labs and the Great Age of American Innovation” by Jon Gertner, which featured this quote:

By the early 1960s, Bell Labs executives had concluded that millimeter waves would serve as the communications medium of the future.

The Idea Factory: Bell Labs and the Great Age of American Innovation

AT&T’s Bell Labs were working with millimeter waves aka “mmWave” in 5G speak, way back in the 1960s, but using waveguides instead of air as the transmission medium.

AT&T saw the vast amounts of bandwidth available in these bands, and were keen to utilize it. So does history repeat? Are there lessons in here about cursed mmWave bands?

At the time, AT&T’s Long Lines network operated a vast point-to-point Microwave network, spanning across the United States. It operated from 3.7Ghz to 4.2Ghz capacity planners and engineers knew, even with the best multiplexing, you were limited to how many channels you could cram into 500Mhz of space, so Bell Labs started looking for solutions.

Almost from the first, however, the possibility of obtaining low attenuations from the use of circular-electric waves, carrying with it, at the same time, the possibility of extremely high frequencies and accordingly vastly wider bands of frequencies appeared as a fabulous El Dorado always beckoning us onward.

G. C. Southworth – Researcher at Bell Labs – 1962

Initially Bell Labs researchers looked at higher frequencies for these wireless links, but after experimenting with using centimeter wavelengths through the air and the issues with attenuation from rain and water vapour, more research was done and Bell Labs decided to use waveguides as the transmission medium for these millimeter wave transmissions, instead of transmitting through the air.

An exploratory development effort was begun in 1959 on a system utilizing 2-inch waveguide and travelling-wave-tube repeater, but was abandoned in 1962 because of TWT cost and reliability problems and because the capacity exceeded then-current Bell System needs.

BSTJ 56: 10. December 1977: WT4 Millimeter Waveguide System: Introduction

Thanks to the recent development of IMPATT diodes and Solid-State devices, it was not abandoned for long, and research was picked up again in 1962. At the time Bell Labs didn’t need the additional capacity, nor did they know when it would be commercially viable to start using millimeter waveguide in the field, but like the 5G operators today, Bell Labs staff had seen the massive amounts of bandwidth available at these higher frequencies, and were looking to exploit it.

The idea at Bell Labs was to send information through such waves not by wires or broadcast towers but by means of the circular waveguide, which had been developed down in Holmdel. “A specially designed hollow pipe,” as Fisk defined it, the waveguide was just a few inches in diameter, and lined inside with a special material that would allow it to carry very high-frequency millimeter radio wave signals.

The Idea Factory: Bell Labs and the Great Age of American Innovation

Unfortunately the physical problems of running waveguides in pits and pipes across the country were immense. After lots of research on novel shapes for Waveguides, bending of waveguides and underground jointing of waveguides Bell Labs staff settled on just digging new trenches for the waveguide and not reusing anything.

Around the same time the first MASERS were coming onto the market, and light (free space optics) was being considered instead of electrical energy as a transmission medium. Test shooting lasers through the air highlighted the high optic losses in air, showing this wasn’t practical as a transmission method. While optic fibres existed at the time their losses were so high as to make transmitting anything over a few meters impractical.

All the millimeter wave transmission in waveguide research culminated in the creation of the WT4 system, in the late 1970s.

A 60mm waveguide was used

Advertisement from the April 12, 1971 issue of Time magazine

Using two levels of Phase-Shift keying they were able to provide 238k concurrent calls of capacity, which they calculated could be doubled by moving to four levels of PSK.

On a 14km test system (Bell labs used SI units), they calculated they had the ability to carry almost half a million concurrent voice calls, and with 274 Mbps of bandwidth (DS-4), which for the 1970s was no mean feat.

AT&T had historically installed cables, but unlike cables, Waveguides can’t bend, so are more akin to installing water or gas pipes.

This meant the installation of the waveguides into the field leveraged processes from the pipeline industry that were adopted for installation of the waveguides.

“Push sites” selected where a steel sheath (which essentially equated to lengths of hollow steel pipe) could be pushed in under the surface of the earth, with extra pipe welded onto the end as it was pushed along.

This created a clear, straight, conduit for the waveguide to be installed. Due to the fragility of the waveguides themselves, they were laid within the pipe on roller bearings to support the waveguide and to help it slide inside the steel sheath.

In tests AT&T were pushing almost 2.5 Km of waveguide in from one site, with extra lengths of waveguide (9m lengths) being joined by the special “waveguide splicing vehicle” and pushed into the sheath.

Repeater stations were equally tricky,
Luckily the WT4 system only required repeater stations at intervals up to 60Km, although when going over hilly terrain, the bends in the waveguide increased losses, so would require repeaters at shorter intervals (~50Km).
The inability to bend the cables required a tunnel under each repeater station, through which the waveguides would run, with the repeaters tapping off the waveguides below, via a network of filters.
Like the microwave network, some of the repeater stations were equipped to add/drop channels, allowing local traffic to be added/dropped off mid-span.
The system was using the new (at the time) Solid State components, but to increase reliability the electronics were encased in airtight dry nitrogen enclosures.

As the WT4 system and its finicky waveguides was being perfected in the 1970s, Corning, a company then known for glass manufacturing, was able to demonstrate that by removing impurities in the glass, optical fibres could be produced with losses of 17 dB per kilometer. Shortly after they got it down to 4 dB per kilometer, and these values kept falling. While early fibre optics were not without their challenges, fibre could be installed in existing conduits, without specialised pipe-pushing and welding equipment, and at a much lower cost per meter.

While WT4 provided bandwidth in numbers unseen before, it’s high cost to deploy and many limitations saw it fade away into the annals of history.

Even in the 1960s Bell Labs staff knew the case for mmWave wasn’t yet financially viable, but built it for a future that didn’t come the way they expected.

So what can this 60 year old tale of engineering teach us?

Bell Labs were pinning their hopes on mmWave to provide limitless bandwidth – and it could, but was faced the ultimate issue of not being financially viable. Here we are 60 years later, and again, many telcos are also pinning a lot of hope on the higher bands.

As was the case in the the 1960s, there is no doubt the bandwidth available for 5G in mmWave is huge (thanks Shannon–Hartley theorem), but it comes with equally vexing challenges to do with propagation and cost of the rollout.

Only time will tell if 5G’s mmWave endeavours end up seeing wide scale adoption.