the message board equivalent to “the number you have reached is no longer in service”.
When I worked at AT&T, I actually met Doug Kerr, one of the guys responsible for the touch tone keypad as we now know it.
There was some work done with different keyboard arrangements for the numbers. One looked at a 2 x 5 and a 5 x 2 grid, and another looked at a circular arrangement. However, what really won the day was the way the tones for the keys were generated. Bell Telephone used what was called a Dual Tone Multi-Frequency arrangement (DTMF). They could use a single transistor to generate both tones. This was important since transistors were about $10 a piece and the standard dial phone didn’t cost more than $15. By arranging the buttons in a 3 x 4 arrangement, Bell Telephone only needed seven tones and they could generate them with a single transistor.
This was done back in the very late 1950s and into 1960. At that time, the old exchange names were being phased out. Your phone number was no longer GReenwood 8-1234. However, the exchange letters were still kept, so your phone number was still GR8-1234 and not 478-1234. Thus, it was still important to keep the phone dial arranged alphabetically. This meant that 1-2-3 were on the top and not 7-8-9 like on a calculator. The 0 was still on the bottom like most calculators though.
About the same time, Bell Labs was developing the first automated PBX which meant that businesses no longer needed an operator to do things like transfer a call to another number, and it was realized that it would be nice if you could have separate command keys to use these options. Thus, next to the zero, two more keys were added: A star and a diamond. This was really no problem because the DTMF arrangement meant that the two tones needed for those buttons already existed in the circuitry.
It was a long time ago, and I can’t quite remember all of the details about the politics Kerr mentioned. But, it basically involved the fact that the star and diamond aren’t standard characters in the ASCII character set. This meant that the user manuals couldn’t be written using the typesetting software AT&T developed. Doug Kerr chose to replace them with the # and * symbols. The * was still referred to as the “star” key in the user manual, but the “#” key didn’t have a name. Somehow the term “octotherp” was coined, and that became a footnote in the user manual.
Later on, Don McPherson called it the octothorpe to honor Jim Thorpe, the athlete. Since McPherson was responsible for training many of the customers, the term octothorpe became better known and was later used in external customer relations documentation.
In 1965–66, my high-school computer class used to go to Murray Hill every other Saturday morning, to play with their IBM 7094 and its three slave 1460s. They had some phones there with an entire fourth column of other symbols—the only one I remember was a diamond. I believe they were used by an experimental dictation service that never went public.
It wasn’t supposed to match the supposed reason for the QWERTY layout. It was in response to your comment to Kevbo’s comment. There is nothing inherent in the layout of 123 at top vs 123 at the bottom that makes it faster, but when you have a reasonable sized segment of the population with a lot of practice typing in one pattern such that they are extremely fast, reversing that pattern will forever throw them in a bind as habituation will drive them to be wrong.
Of course, that couldn’t keep someone else from developing habituation to the new layout, or conceivably someone adapting the ability to speed type in either layout, but the principle is that people spend far less time dialing numbers than they did doing numerical entry for accounting purposes.
And again, I’m not saying it is a true reason, I am saying it is a consistent explanation.
I fail to see how physical layout of the buttons affects electrical wiring underneath.
This is the more reasonable explanation. With a 3 x 4 grid, putting the letters alphabetically top down gives the standard layout. Alternately, the numbers could be arranged alphabetically starting at the bottom, but that might be less aesthetic.
Those with four rows of buttons were usually sold to the military. These were the Autovon phones.
Each row had its own unique tone and each column had its own unique tone. Pressing a particular button selected both the row and column tones.
The tones generated were different frequencies ranges for the row and columns. Somehow, this allowed for all tones to be generated with a single transistor back in the late 1950s when the system was created. As a bonus, the dual tones somehow made the system more robust.
Speaking as an engineer, I can see it well. Think of a matrix, where you have three lines vertically, one running down the 1-4-7-* column, the next under 2-5-8-0, etc. Then you have another set of lines running horizontally, the first under 1-2-3, then 4-5-6, etc. Each row generates one tone (one of the Dual Tone Multi-Frequency pair), and each column, another, single tone. One tone from a row and one tone from a column makes two tones, or DTMF.
Sure, nowdays there are other ways to do this with computers, but in 1958, hardware was far less sophisticated and far more expensive, even for simple tasks.
If you have an old TT phone (this won’t work on new ones), try pressing 2 buttons in one row or one column. You will get a single tone, the one that is common to both buttons. That is one way we used to play tunes, by eliminating one of the double tones.
And to add to the excellent and interesting post by qazwart, it is not just a 3x4 matrix, but 4x4, or 16 possible tone combinations, 4 of which are not available on a standard telephone keyboard. I don’t know if the ABCD ones were added later, but I suspect they were part of the original concept much like the * and # buttons were.
I played with this many years ago, and you can buy DTMF generating and decoding chips for OEM applications or just tinkering. They always include 16 code pairs; it is up to the equipment designer to decide which ones to use, and for nonstandard (non-POTS) applications, what each pair represents on the receiving end.
They were used by the (now defunct) military AUTOVON phone system, and they were also used for various PBX and Centrex systems for miscellaneous tasks.
Some older PBXes that are still in service will do interesting things if you feed them some 4th-column tones.
So it’s a physical implementation issue, not an electrical connectivity issue.
Because you can assign the functionality with the same 4 x 4 grid layout, but wire it differently, and put the display with the buttons
69241035#*BDCA
and it will work the same way. It’s all about how the wires are connected underneath.
I had a Staff Report in the works (before they were discontinued), that discussed the Touch Tone system and the A-B-C-D row. Let me see if I can find it and link you to some references about it. And yes, the Autovon system is the correct answer.
OK, here’s excerpts from the Staff Report including a very interesting link:
The engineers who designed the Touch-Tone system originally envisioned it in the 1940s as a multi tone system. The familiar dual-tone system in use today (called DTMF for “Dual Tone Multi Frequency”) came about when engineers realized that a four by four grid consisting of two simultaneously sounded tones of discrete non-harmonically related frequencies would be not only more reliable, but more secure. A four by four grid had to be used, as a three by three grid would have only allowed 9 numbers. And you can’t let 6 good tones go to waste! Eight tones are used in the grid, which is as follows:
1209 Hz 1336 Hz 1477 Hz 1633 Hz
697 Hz 1 2 3 A
770 Hz 4 5 6 B
852 Hz 7 8 9 C
941 Hz * 0 # D
For instance the “8” key is located in the second column and the third row of the keypad. The frequency assigned to this column is 1336 Hz. The “8” key also belongs to the third row. The frequency assigned to this row is 852 Hz. So when this key is pressed, both frequencies are triggered resulting in a dual tone beep.
The letter keys (A, B, C, and D) are still in use today, but only for specialized applications. Technicians use them for network troubleshooting and applications, as do amateur radio operators for special controls on their systems. Those keys are available on several of my amateur radio units, and they get some use controlling several radio repeaters in my hometown.
As is usual in any new development, the government wanted to get involved in this and asked that the phone dial be expanded for special services. The result was a device called the Autovon phone system, only used by the Department of Defense and the White House. In this system the numbers 1 through 0 were supplemented by several keys to do special things within the local PBX network. Allowing important traffic to get through every time, the levels of priority available were Flash Override (A), Flash (B), Immediate (C), and Priority (D), with Flash Override being the highest priority. Pressing one of these keys before you dialed your number gave your call priority, overriding other conversations on the network. Pressing C, Immediate, before dialing would make the switch first look for any free lines, and if all lines were in use, it would disconnect any non-priority calls, and then any priority calls. The A key, Flash Override would kick every other call off the trunks between the origin and destination. This system is defunct now, as advances in electronic PBX systems have made the need for these keys irrelevant. The last hold-out was the White House, leaving this system in place until the late 1990s.
To see an original Autovon dial, and to hear the touchtones, head on over to http://www.porticus.org/bell/telephones-technical_dials-touchtone.html –- you’ll find loads of good information there, including the original press release from 1964 announcing the new technology.