I am sure the answer is "it depends", so the better question is: To what extent is this possible?
The calls in question were made in the 70s, so we are in luck there. One of them can be heard here:
JFK Facts:
CNN Channel in YouTube
TIA
-Ramon
If there is any echo then the time delay will be related to the distance. Even if there is no echo, this itself provides useful information, as local calls did not in those days use echo cancellers, whereas some long-distance ones did, depending on the distance. If the echo has a very short latency, it will not be audible as such, but here may be a notch in the frequency response, the frequency of which will be indicative of the delay.
John
Circa 70's, era of 'Kaptain Krunch" *if* the call were made 'inside' the office switch range, the bandwidth is incredible.
For example, across Silicon Valley, we could routinely send 10kbits/specd, and higher, using a modem with a simple wquare wave the bandwidh was so good! But if linked into carriers and trunkines that bandwidth was stripped to a standard 300-3kHz bandwidth, with a 4-6 pole cutoof, and could NO longer use the modem waveform system.
It is my undertanding that now the equipment strips the bandwidh no matter where.
PS: I met, worked with the guy, that made/sold those infamous "Blue Boxes" that enabled you to call around the world for free. He is a convicted felon and spent 1 year in jail. I asked him, "How do you call for free?" He said, "*IF* I tell you , I will be committing a felony. and *IF* you listen, YOU will be committing a felony." That's when I learned that because he had been so severely punished AND there were so many laws affecting citizenry, that the streets were SO much safer at night.
What is the purpose of this exercise? Bill O'Reilly obviously was in Dallas. Why would he be talking about getting a flight if it was a local phone call?
-- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
While the blue colored were the most famous, they actually came in more colors than M&Ms (or the candy Macintoshes).
I read somewhere that phreakers Jobs and Wozniak even phoned the Vatican, claiming that the caller was the president of the US. Some Cardinal was summoned and they had to hang up quickly.
-Ramon
You forgot red. Black was easily defeated by the CO (e.g., moving to ESS). Red and Blue were, by far, the most "useful".
Yes, but I'm not going to get involved in a conspiracy theory resurrection.
In the 1970's all long lines telephony was analog. There were channel bank filters and mixers that upconverted base band audio to higher frequencies for transmission, and back down at the destination. Also known as FDM (frequency division multiplex: The conversion process is not perfect and it is possible to see mixes and intermodulation products of the carrier and local oscillator frequencies of this up/down conversion process on the resultant audio[1]. There was also about a 1 to 5 Hertz Bode frequency shift introduced to prevent feedback and oscillation. You can't hear the beatnotes and frequency shift, but you can see them with PC based spectrum analysis. I suggest: or better yet Spectrum Lab: You will need to look at the "blank" spaces between the words, where there is no voices or background noises to muddle the display. You're looking for continuous carriers, buried well under the voices. Autocorrelation: is a big help for seeing these tones by removing the audio and background rubbish.
Interpreting the residual tones, and separating them from recording artifacts, is going to be difficult. You'll need to find someone with experience in 1970's telco muxes as well as some clue as to where these recording have been, whether they were converted from previous recordings, and possibly what equipment was used. You'll also need to know which CO handled the call, which will point to which carrier handled the call (AT&T, GT&E, ITT, etc), and then what brand and model of carrier equipment might have been used. That's not going to be easy and will probably be a huge time burn for little benefit.
Hopefully, I've given you enough hints to get started. You're on your own. Don't bother sending me email as I won't help.
[1] I still do some of this looking for residual PL/DCS and control tones on stuck FM land mobile and public safety transmitters to identify the culprits. Since the frequency of operation is known, that limits the likely culprits to known licencees and a known list of equipment. However, the introduction of digital radios has made this technique both too difficult and no longer necessary due to built in transmitter ID.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Just like e-mails, ALL OF IT can be faked. Or any combo. Name, number, voice, sound real or sound recorded, static, backgrund sounds, etc.
"Echos" can also be faked; was done at least once i know of 40-50 years ago. Time delay "put" caller in Great Britain and reality was in next room.
If you cannot figure out a possible rational explanation, then you are LOST.
Yeah, that sounds good, but won't work.
Ma Bell began deploying echo cancellers on long lines in about early
1980's and on local loops until they had all digital switches in the late 1990's. Northern Telecom switches saw them initially in about the mid 1990's. You can generally assume that 1970's switches did NOT have echo cancellation.Echo cancellers are designed to reduce the echo to the point where it is no longer audible. As I vaguely recall, it's somewhere between -20 and -30dB below normal 0dbm telco audio. At -30dB below peak, you generally can't hear anything, although it will vary because human hearing frequency response is not flat. However, you can see the echo on a scope, spectrum analyzer, autocorrelator, or other instruments because the base noise level is usually around -40dB or lower giving you about a 10dB range to work with.
In the 1970's, the echo problem was generally caused by the 2 wire to
4 wire transition. In the typical circuit, there were at least two of those to every connection, usually where the 2 wire local loop hits the 4 wire switch at the CO (central office). The hybrids (transformers) at these points reflect some of the signal back to the source, causing an echo. Anything over about 10 msec is noticeable and over 50 msec is obnoxious.If you assume that the entire delay happens at the speed-o-light over the trunk wires, 50 msec is: 1/2 * 186,000 mi/sec * 50*10^-3 seconds = 4,650 miles of wire. (The 1/2 is because the echo signal needs to go up the wire, reflect, and then back again). If the long line wires were the only sources of hybrid echo delays, POTS echo would not be a problem because the USA is only 2,500 miles wide.
So, if not the wire, where does the 50 msec delay come from? It's all the electronics, equalizers, and loading coils along the lines. These are totally unpredictable, unless you have an accurate measurement of the in/out delays of all the central offices of the 1970's. Different switches also have different delays. Oh yeah, there's the velocity factor of the various wiring systems. 1970's also means microwave links, which also add their delays.
In other words, even if you could measure the delay from the recording accurately, you could not even come close to measuring the distance between the two central offices involved (plus the "last-mile" to the callers instruments) because you don't know the delays added by the various devices along the route.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Last time I measured echo return loss on phone lines (around 10 years ago) there was no sign of echo cancellers on analogue lines connected to digital switches in the UK. The echo mostly came from the hybrid in the phone itself and from acoustic coupling in the handset. Typical return loss values were around 20dB. (I wrote an analysis module for asterisk which automatically measured ERL, echo latency and various other parameters for quantifying call quality. This was used for testing handsfree mobile phone devices.) ...
But you do have a good chance of determining whether it is a local or "long distance" call which was the original question.
John
That's no revelation, Bob: The younger generation has no idea that something called "Usenet" even exists.
A few years back, it was possible to access it for free (via Google Groups) and post links to it (which is essential for its survival).
However, with their new interface, Google inflicted yet another wound to Usenet. Being a pioneer and co-founder (along with a DeMillean "cast of thousands") back in my days at MIT, it saddens me.
Best regards,
-Ramon
Showing my age here, but the Blue Box stuff happened when I was an undergrad. One of my buddies heard that it was all based on an article in some Bell Labs journal that divulged the trunk access tones, and also heard that Bell was quietly removing copies from college libraries. (This was before the Internet, of course!) Anyway, he guessed that they may not have gotten to the backwaters of General Motors Institute, so he checked... bingo!
So now, somewhere in my files, I no doubt still have my copy of said infamous article. I never tried to put it to use, however... heck, I didn't know anybody far enough away to need long distance calls!
Best regards,
Bob Masta DAQARTA v7.60 Data AcQuisition And Real-Time Analysis
Den torsdag den 12. marts 2015 kl. 14.42.29 UTC+1 skrev Ramon F Herrera:
you can still access it for free via Google groups,
and you can post links to a post:
or
-Lasse
On a sunny day (Thu, 12 Mar 2015 08:28:30 -0500) it happened Ramon F Herrera wrote in :
Nice to hear you were part of that. I did notice that some years ago universities were the first to switch off their servers. There are still many free news servers where you can post too, aioe.org being a well known one. I sometimes use google to backtrack to an original posting.. Google is not really Usenet, and they named it 'google groups' on top of that. I wrote my own news reader in 1998 or so because there was no Free Agent for Linux.
Yes, I guess it is possible. A few weeks ago, in a Forum, I posted some URL pointing to Usenet (Google Groups) but it did not work for Internet Explorer users. I just tried it and it works now.
-RFH
Right. ALL the required information was in the public domainn.
What caused it to 'hit the fan' that the playfulness got out of hand. The people would 'stack' trunk lines in and out of cities, then call ATT 'inspector' employess like at 2:30 am and say listen to this, then hang up and the now wide awake victim would listen to the clicks as each trunkline relinquhed, click, click, click, ... sometimes stack 20+ That was 'playful' irritation, but what really brought down the rafters, was a group stacked trunklines in and out of Salt Lake City, essetially isolating it completely! With the potential of emergency calls being shut off [and perhaps some were shut off], the govt stepped in and stopped it all. [that's my understanding] Yes, you can find a small reference to the isolation occuring in the public domain as a general news media blurb. I remember the announcement, but not attaching significance to it, until I met ?? and he told me about the incident from an 'insiders' point of view.
But it's not within the same office. O'Reilly is saying he's going to take a plane and come down there tomorrow. Sounds like O'Reilly was in NY, or at least clearly he was somewhere out of state.
I agree, that tape is remarkably clear for something long distance in the 70's and that was also then recorded on tape, played back, etc. We don't know what the connection between recorder and phone was either. But since the investigator was doing the recording and he was traveling, in FL at the scene, reasonable to assume it's probably a suction cup magnetic pickup. That would further compromise the quality. And IDK who goes to all the trouble of recording all their routine calls like that when traveling, preserving them for 40 years, etc.....
It could be real, but who knows. If O'Reilly is lying, it would be a case of lying for little apparent gain. I don't think whether O'Reilly was there or not really adds much.
My understanding of POTS phone technology is that it was sampled at 8Khz, which means it had a max bandwith of 4khz, and effectively it was more like about 3khz.
Not MIT! The server news.mit.edu was one of the first, most active and it is still around. See here:
(scroll to "Usenet")
-Ramon
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