Telephone Ideas for a Raspberry Pi 2?

[bellsystem]

I might be getting a free Raspberry Pi soon if I can show that I have a proposal and plan for it laid out.

Basically, I was hoping to use the Pi for C*Net
I've since learned that would be impractical for my situation.
Being the telephone guy I am, I decided I would find a different usecase for the Pi, instead of doing something boring and useless with it.

My ideas were tone generator and P2T converter, but I've learned elsewhere that it is impractical to build your own P2TC.
And I've heard here that apparently it's not so easy to use a tone generator, let alone build one.

And I don't yet know if it would be useful to install Asterisk on the Pi and then hook it up the PBX without connecting it to the Internet, although I feel like I might be able to do something cool with it (dial 9 from a PBX to get to the Pi and hear a recording, etc.) if that is possible and feasible. I thought it might be cool to turn the Pi into a "station" of some sort. For instance, hook it up to either a standalone phone (in which case it would have to power the phone) or connect it to a PBX CO line (in which case it would not have to provide dial tone). And maybe have some sort of setup where if I dial 9 from the PBX I get into the Pi and it says For x, dial 1; For y, dial 2. One useful thing I could program might be Time and Temp. from the Internet (dependent on an RJ45 connection) but I would like some features to work without network connectivity.

Better yet, is there really any reason I can't have the best of both worlds? I could hook the Pi up to a PBX and also have a line coming out of it - say going to a cable phone RJ11 connection or something. I could have Press 4 for Time and Temperature and Press 5 to use this Raspberry Pi as a P2T converter. And maybe another option to access the outgoing line without using it as a converter. I wouldn't be able to use it as a physical interface though, in this case (i.e. tone generator). Just a thought. I doubt anything like this exists and I bet it would make a cool project (if I could get it working).

But I've never used Linux before, let alone the Raspberry Pi, so I'd like to hear what other people think before I decide to do something I may not be able to do successfully.

If anyone has any suggestions for what I should do with my Pi, that would be welcome.

[Alex G. Bell]

I might be getting a free Raspberry Pi soon if I can show that I have a proposal and plan for it laid out.

Basically, I was hoping to use the Pi for C*Net
I've since learned that would be impractical for my situation.
Being the telephone guy I am, I decided I would find a different usecase for the Pi, instead of doing something boring and useless with it.

My ideas were tone generator and P2T converter, but I've learned elsewhere that it is impractical to build your own P2TC.
And I've heard here that apparently it's not so easy to use a tone generator, let alone build one.

And I don't yet know if it would be useful to install Asterisk on the Pi and then hook it up the PBX without connecting it to the Internet, although I feel like I might be able to do something cool with it (dial 9 from a PBX to get to the Pi and hear a recording, etc.) if that is possible and feasible. I thought it might be cool to turn the Pi into a "station" of some sort. For instance, hook it up to either a standalone phone (in which case it would have to power the phone) or connect it to a PBX CO line (in which case it would not have to provide dial tone). And maybe have some sort of setup where if I dial 9 from the PBX I get into the Pi and it says For x, dial 1; For y, dial 2. One useful thing I could program might be Time and Temp. from the Internet (dependent on an RJ45 connection) but I would like some features to work without network connectivity.

Better yet, is there really any reason I can't have the best of both worlds? I could hook the Pi up to a PBX and also have a line coming out of it - say going to a cable phone RJ11 connection or something. I could have Press 4 for Time and Temperature and Press 5 to use this Raspberry Pi as a P2T converter. And maybe another option to access the outgoing line without using it as a converter. I wouldn't be able to use it as a physical interface though, in this case (i.e. tone generator). Just a thought. I doubt anything like this exists and I bet it would make a cool project (if I could get it working).

But I've never used Linux before, let alone the Raspberry Pi, so I'd like to hear what other people think before I decide to do something I may not be able to do successfully.

If anyone has any suggestions for what I should do with my Pi, that would be welcome.

Actually, the aspects which would make it "impractical" to perform P2T conversion with an R-Pi would be just as present for almost any telephony application:  The problem of properly coupling signals from the possibly grounded electrical environment of the R-Pi logic system to a floating balanced telephone line.  It's also a fundamental requirement, essentially a "generic task" for almost anything you might want to do in analog telephony.  It's one of the many functions of an ATA.  So it's a bridge you will need to cross if you have a serious interest in working in this realm.

The actual P2T aspect itself is rather trivial.  While on one hand it might be seen as a wasted effort since it would be "reinventing the wheel", as a learning exercise it would be very much the opposite: a worthwhile self-educational task.  We all have to crawl before we walk or run.

[bellsystem]

Yes, I know there are P2T converters out there but they seem limited and hard to come by (and don't always work with all types of lines). I'm getting the Pi for fun to screw around with, so I don't mind reinventing the wheel for learning experience.

The problem of properly coupling signals from the possibly grounded electrical environment of the R-Pi logic system to a floating balanced telephone line.  It's also a fundamental requirement, essentially a "generic task" for almost anything you might want to do in analog telephony.

So, you're saying I need an ATA if I want to interface/somehow connect an analog phone or PBX with the Raspberry Pi AT ALL, period?

[Alex G. Bell]

Yes, I know there are P2T converters out there but they seem limited and hard to come by (and don't always work with all types of lines). I'm getting the Pi for fun to screw around with, so I don't mind reinventing the wheel for learning experience.

"The problem of properly coupling signals from the possibly grounded electrical environment of the R-Pi logic system to a floating balanced telephone line.  It's also a fundamental requirement, essentially a "generic task" for almost anything you might want to do in analog telephony."

So, you're saying I need an ATA if I want to interface/somehow connect an analog phone or PBX with the Raspberry Pi AT ALL, period?

An off the shelf P2T converter may be hard to come by but one could be built from relatively simple easy to find logic chips without the complexity of a firmware based implementation.  Regardless, I think you would learn a lot by doing it.

No, I didn't say that. I said: "It's one of the many functions of an ATA."  A subset of functions is not equal to the whole. 

An ATA performs the interface from a digital logic system which may be grounded to a floating balanced analog environment (which inherently must not be grounded), among many other much more complex functions it performs.  You need to reproduce or procure hardware which performs these interface functions. 

Devices such as a 1001 type data coupler is an example of a device produced to allow a grounded customer owned computer system or modem to control a phone line.  If you google around you'll probably find technical references.

[bellsystem]

What does whether a system is grounded or not have to do with connecting them? Am I risking a power surge or something?

[Alex G. Bell]

What does whether a system is grounded or not have to do with connecting them? Am I risking a power surge or something?

Asking that question indicates you don't understand fundamental electrical concepts.  Read Automatic Electric Training Bulletins 800 & 801 (or maybe it's 801 & 802): electrical and mechanical principles of telephony.   Also find and download AT&T's "Principles of Electricity and Magnetism Applied to Telephone and Telegraph" (or something like that).

[TelePlay]

What does whether a system is grounded or not have to do with connecting them? Am I risking a power surge or something?

A quick primer "in general" before doing what Alex suggested.

     http://www.aptsources.com/resources/pdf/Floating%20Output.pdf

[bellsystem]

Correct, I don't have much of an interest in electricity beyond AC vs. DC.

Well, I read the Floating Output PDF. Didn't really learn much. I do know that grounding is important. On a sidenote, Panasonic has very explicit instructions to use a grounding rod for its PBXs but neither of my PBXs are grounded. The electrical socket already has the middle plug anyway - I imagine that is functioning as a ground of some sort. And if it's not, oh well.

I have the 1953 of PEMAT&T - will that suffice? I've been looking for other editions but it seems that's all that people have managed to scan of late.

Can you point to an AE repository, or the Bell System equivalent? This is all I can find - Bulletin #815: http://www.pdfs.telephonearchive.com/gsps/

[TelePlay]

Correct, I don't have much of an interest in electricity beyond AC vs. DC.

With all that you seem to be thinking of doing, unless you understand electricity and the basic components to control or use and measure AC and DC alone or in a circuit, you will end up ruining a lot of equipment.

As for BSPs, there are many at TCI.

     http://www.telephonecollectors.info/

This simple search for you turned up many sources of BSP's.

     https://www.google.com/#q=bell+system+practices

[Alex G. Bell]

Correct, I don't have much of an interest in electricity beyond AC vs. DC.

Some sincere advice you should take to heart: Based on the above statement you have chosen for yourself a path which dooms you to not succeeding with the things your ask about.  None of this works by magic.  It works because many people carefully went through a meticulous thought process and built on the achievements of others.  As the cliché goes (completely appropriate here for the attitude you have expressed): "You can lead a horse to water but you cannot make it drink".

Well, I read the Floating Output PDF. Didn't really learn much. I do know that grounding is important. On a sidenote, Panasonic has very explicit instructions to use a grounding rod for its PBXs but neither of my PBXs are grounded. The electrical socket already has the middle plug anyway - I imagine that is functioning as a ground of some sort. And if it's not, oh well.

Safety grounding has nothing to do with grounding required as part of the signal path.

I have the 1953 of PEMAT&T - will that suffice? I've been looking for other editions but it seems that's all that people have managed to scan of late.

Any issue would suffice.  AFAIk 1961 was the last.

Can you point to an AE repository, or the Bell System equivalent? This is all I can find - Bulletin #815: http://www.pdfs.telephonearchive.com/gsps/

Already did.

[Victor Laszlo]

Correct, I don't have much of an interest in electricity beyond AC vs. DC.

Then you have chosen the wrong hobby, and you are wasting the time and good nature of those of us who have given you a second chance, and are trying to help nurture your interest and progress in the art of telephony.

There are many other electrical concepts beyond AC and DC that are absolutely essential to telephone theory.  Resistance, capacitance, inductance, impedance, voltage, current, gain/loss, reactance, reluctance, crosstalk, grounding, bonding, coupling, balanced/unbalanced, to name a few. Relegating these concepts to the "I have no interest in..." pile is doing yourself, and us, a disservice. You, because you demonstrate a lack of dedication, and us, because we have better things to do than to try to encourage a dis-interested student.

I privately postulated to a few folks here, during the last go-round with you, that possibly there was a troll-like theme to your Q&A.  I now am convinced.

Further, beyond the small world of telephony, it is also recommended to anyone even remotely involved in any electrical endeavor, that they understand the difference between GROUNDING and GROUNDED conductors, and how that distinction is applied to safety and correct operation of everything electrical that we come into contact with in the real world. You are advised to start studying THAT right away. The knowledge can only help you in the future.

[Victor Laszlo]

. . . I imagine that is functioning as a ground of some sort. And if it's not, oh well.

Some more fatherly advice: if you happen to be sitting across a table from an arson investigator some day, try not to adopt such a blasé attitude.

We were all, probably, at some point in our lives, "angry young men" but we got over it.  You should try.

[bellsystem]

I've decided to pursue something with telegraphy rather than telephony for my Raspberry Pi.

This sounds like a cool project: http://kylegabriel.com/projects/2016/02/morse-code-translator.htm

Thanks for the ideas all.

[Victor Laszlo]

Excellent choice. Goodbye.