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Beep Beep Line - Talking Conference over CO Busy Signal

Started by Dennis Markham, October 14, 2009, 09:28:51 PM

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Reply from the Guru:
A very common old time conference line

Busy Signals were generated by one interrupter.... distribution was by a resistive network.

Best example:  An amplifier, a few watts has a 600 Ohm output. EACH connection to the amplifier, and there may be hundreds, or just 10 (each being one rack) is connected by one resistor to the tip and one resistor to the ring.

This is a simple manner to distribute the audio, every once gets connect, but with a small value resistor. This way they are somewhat isolated, but not totally. If one short occurs it is really just a resistor across the amplifier and nothing happens, well perhaps a slight decrease in volume. The assumption was, in the early days, nobody would talk during a busy signal and with the resistors for each "path" there was a reduction in the talk volume between paths

So it became necessary to shout into the line, talking a normal volume was a bit low.

It would be better to use an amplifier that had an output resistance of ... say 16 ohms, then to use two each 330 ohm resistors to each path, this would mean the only common connection between paths would be the 16 ohms of the amplifier to "talk over" and it would have been near impossible. Actually in practice one isolation set of resistors would serve one bank of connectors in a step office, so anyone on that bank could easily talk. And the 16 ohms was probably 600 ohms, so that made it a lot easier to talk over.

In the early days it was felt that the Z had to be a nearly perfect match. This is not quite so in practice and severe mismatch between circuit is not usually a problem. It is if you have amplifiers and repeaters, but even so a mismatch is often not an issue.

-Bill G

Dennis Markham

Bill, thank you and your Guru.  I guess it's just easier to remember it as the beep-beep line.  I'm sure Jorge understands all that electrical stuff.  I appreciate you asking your friend about it.  I kinda sorta understood some of it, maybe. :)


I never knew about any Beep Beep system.  That would have been fun.

I do remember the blue boxes.  As I recall, there was a guy who went by "Captain Crunch" who was a notorious blue box user.  I don't know if they ever caught him.  I think he "operated" out of the San Luis Obispo area in California.



I don't think that I saw a reply to Dennis' question "What brought this to an end".

I recall us doing "Talk over Busy Mods" in the Strowger CO's around Vancouver, probably in the late 70's. That brought the Conference Calls to an end here!



Quote from: bwanna on October 15, 2009, 06:15:10 AM
briny, i had not heard of the beepbeep line until i read about it on dennis website a while back. you & i must have been nice well-behaved children. not the type of hooligan who was  looking for ways to cause trouble & foul up the phone co. :D
I, too remember it. It was amazing to see how many people used it at any one time. Great fun!

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Hello everyone!  I'm the guy who posted the audio clip over at Dennis' other web site about Rotary Phones.  I also was a Jam Line (Beep Line) addict for several years starting in High School.  I was reading the technical description of how it happened here with some interest.  It is quite different from what I was told by the local Phone Phreakers in Minnesota.  The explanation here was Ma Bell was experimenting around with Electronic Switching (ESS) so they could convert all their old equipment from mechanical relays.  In order to do this right, Ma Bell would hook in the ESS prototypes in parallel with the existing exchange step-offices.  In doing this, it created an internal loop in the lines that created the ability to talk across the busy signal.  Here in Minnesota in the 1970's, Jam Lines were usually confined to one or two prefixes at any one time, and they came and went for over a decade while the phone company perfected the ESS switching we take for granted today.

Near as I can tell the Jam Line got it's start here in the Twin Cities area when the local Rock radio station started using Request Lines for callers to call in and win stuff.  The first caller got through to the DJ, and the rest would get the Jam Line.  How many people could get the Jam Line was dependent on how big the relay exchange office was, but usually was limited to about 20 callers before the circuits became overloaded and crashed the trunk line, forcing Ma Bell to reroute traffic.

Of course, when crashes started happening on a regular basis, Ma Bell would send someone out to investigate and the Jam Line would be "turned off."  Fortunately for us here in the Twin Cities, we had the benefit of two unique phenomenon:
1.  All the regular Jam Liners knew all the Ma Bell test lines.  We called these "Loop Line" or some called them the "Hot Line."  For more information on this topic see this entry in Wikipedia:

What our local Phone Phreakers would do after a Jam Line was shut down was head down to the local library and sit down with the City Directory.  They would then choose the telephone Prefix they wanted to start the next Jam Line on, and look for gaps in the sequence of phone numbers listed.  Whenever they saw a break in sequence they would write that number down.  After collecting several "unassigned" telephone numbers they would go home and call them to see if any were "perpetually busy."  When a number wasn't assigned here in the Twin Cities, it would either have a recording saying it was out of service, ring and ring with no answer, or be busy.  It was the ones that were busy they took note of.  After verifying an unassigned busy number worked as a Jam Line, the Phreakers would then make a quick tape-recording running on a loop saying, "The new Jam Line number is: XXX-XXXX" and call up one of the Loop Lines and leave the recording playing over and over again for a few days.....
2. The second thing the Twin Cities had going for it in the 70's was it had the largest geographical toll-free calling area in the world!  We still have the largest toll-free calling area in the USA to this day.  Back in the 1970's, this large toll-free calling area coupled with the second largest subscriber base at 1.2 million, made it a Jam Line paradise.
The recording posted on Loop Line would spread like wild-fire through the high schools by word of mouth, and within days a new Jam Line would start to emerge.

In the 1960's the Twin Cities had sporadic Jam Lines from as early as 1962, through 1970, which were dependent on which radio station request line prefix happened to be hooked in parallel with ESS at the time.  By 1971 through 1984, it was all Phone Phreaker driven using the Loop Lines.  The last Jam Line in the Twin Cities was started by me in 1984.  In early 1983 my mom had received notice that Custom Calling would become available in our area the next year.  I went down to the local library and started collecting unassigned phone numbers and when the Jam Line we were using went deaf, I was ready!  Unfortunately, the final death of the Jam Line in Minnesota was the result of a deadly tornado.  I've posted that story here:

After that I thought the Jam Line would forever just be a fond memory of my youth, until I found our Host's first web site about vintage phones where I was asked if he could post a small audio clip of an old Jam Line tape recording I had made back in 1977.  That small sound bite caught the attention of a local news reporter for Minnesota Public Radio, (MPR) who herself had called the Jam Line as a young teenager here in the Twin Cities.  It took her awhile to track me down, but she was successful and just after Christmas MPR did a special news report on the Twin Cities Jam Line complete with audio clips from my old recordings.  You can read about it here, and listen to the actual broadcast as it has been archived on the MPR site here:

Don't forget to click on the "Featured Audio" link!

Thanks for reading,
Any girls out there?--=BUZZ=--..........--=BUZZ=--.........

George Knighton

Quote from: Phonesrfun on October 15, 2009, 12:05:22 PM
Reply from the Guru:
A very common old time conference line

Busy Signals were generated by one interrupter.... distribution was by a resistive network.

Best example:  An amplifier, a few watts has a 600 Ohm output. EACH connection to the amplifier, and there may be hundreds, or just 10 (each being one rack) is connected by one resistor to the tip and one resistor to the ring.

Ahhh haaaaa......

Typical SNAFU.

Whatever system you roll out, you will never fully appreciate just how people will use it in some fashion you did not intend.
Annoying new poster.


There is a new Facebook group started up for everyone who used to call the telephone Beep Lines:
Any girls out there?--=BUZZ=--..........--=BUZZ=--.........


More useless trivia, Farmington Michigan, the Greenleaf exchange, the number was 476-9999. Don't ask me why I still remember this from the mid 60's. It just all came back to me while reading this thread.