ScottyDoesKnow
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Answer a landline

Sat Feb 15, 2014 1:52 am

Basically I was wondering if it was possible to plug a telephone line into the ethernet port of my raspberry pi, then answer any call that comes in and play a key tone (to buzz them in). I've done some searching but it's hard to find information for my unique case. I've been looking at the java JTAPI, but all the information seems to be talking about managing phones on the network.

Anyone know if this is possible? The language doesn't matter, it's a personal project so just another chance to learn new things.

doormatt
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Re: Answer a landline

Sat Feb 15, 2014 6:03 am

This isn't possible in the slightest.

Ethernet and Telephone systems are completely different, only the jack is similar.

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FLYFISH TECHNOLOGIES
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Re: Answer a landline

Sat Feb 15, 2014 6:26 am

Hi,
ScottyDoesKnow wrote:Basically I was wondering if it was possible to plug a telephone line into the ethernet port of my raspberry pi,
Word "landline" doesn't describe much...
VoIP is based on computer networking, so you don't burn anything if you plug VoIP connector into ethernet port. If your "landline" is anything else, then you don't want to plug it in into the ethernet port.
ScottyDoesKnow wrote:Anyone know if this is possible?
Visit page: http://www.raspberry-asterisk.org/


Best wishes, Ivan Zilic.
Running out of GPIO pins and/or need to read analog values?
Solution: http://www.flyfish-tech.com/FF32

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DougieLawson
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Re: Answer a landline

Sat Feb 15, 2014 8:23 am

Telephone lines run at 50V AC when the bell rings that should fry your RPi nicely and quickly. Telephone lines are NOT ethernet. Telephone lines are still analog. In many countries it is illegal to connect non-approved equipment to the telco's system (it is in the UK).

To connect one to your RPi you NEED a USB modem.
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PiGraham
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Re: Answer a landline

Sat Feb 15, 2014 9:50 am

DougieLawson wrote:Telephone lines run at 50V AC when the bell rings that should fry your RPi nicely and quickly. Telephone lines are NOT ethernet. Telephone lines are still analog. In many countries it is illegal to connect non-approved equipment to the telco's system (it is in the UK).

To connect one to your RPi you NEED a USB modem.
A modem, yes, but it need not be USB. Modems used to be serial port devices.

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DougieLawson
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Re: Answer a landline

Sat Feb 15, 2014 10:03 am

PiGraham wrote:
DougieLawson wrote:Telephone lines run at 50V AC when the bell rings that should fry your RPi nicely and quickly. Telephone lines are NOT ethernet. Telephone lines are still analog. In many countries it is illegal to connect non-approved equipment to the telco's system (it is in the UK).

To connect one to your RPi you NEED a USB modem.
A modem, yes, but it need not be USB. Modems used to be serial port devices.
If you do it on the GPIO pins there are three problems:

1. GPIO is TTL, RS232 modems are anything from 5V to 26V so you need a MAX3232 chip to convert to TTL.
2. The RPi is pre-configured to have a serial console on the UART pins (for some unknown reason designed to make life unnecessarily difficult)
3. There's no RTS pin on the UART, modems usually need RTS

So using a USB modem (as long as it is NOT a crappy Conexant Winmodem) becomes desirable as it solves those three problems in one hit.
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redhawk
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Re: Answer a landline

Sat Feb 15, 2014 10:08 am

Answering calls with a modem is the easy part, actually putting audio tones or sound onto the phone line is going to be tricky without some dirty hacks.

Richard S.

mikerr
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Re: Answer a landline

Sat Feb 15, 2014 10:50 am

redhawk wrote:Answering calls with a modem is the easy part, actually putting audio tones or sound onto the phone line is going to be tricky without some dirty hacks.
It's easy when a modem does all that for you :lol:


Note many USB modems rely on the windows drivers do act as a DSP - these won't work in linux /pi

So serial modems may be a better bet.

I do have a Zoom 3095 usb modem here that has a DSP, and works fine on the Pi (but doesn't recognize UK callerID)
someone else has used the US robotics USR805637 with the pi and that does support UK (BT) CID:
http://www.amazon.co.uk/gp/product/B0019LZCEI/
http://www.amazon.co.uk/gp/product/B005C4680A

also check this thread:
http://www.raspberrypi.org/phpBB3/viewtopic.php?t=23359

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redhawk
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Re: Answer a landline

Sat Feb 15, 2014 11:15 am

Well yes I know modems can beep but I was under the impression the OP wanted to transmit customised tones like the Nokia ring tone or something.
I don't believe AT commands support such tasks and hacking the DSP maybe more trouble than it's worth.
A hardware mod on the isolator transformer coil maybe a possibility to inject analogue audio or pulses from the GPIO into the phone line.

Richard S.

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DougieLawson
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Re: Answer a landline

Sat Feb 15, 2014 11:20 am

Doing any phreaking with phone lines is ILLEGAL in most countries. Even connecting unapproved equipment is ILLEGAL.
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PiGraham
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Re: Answer a landline

Sat Feb 15, 2014 11:37 am

A voice modem should do what the OP wants.

Switch to voice mode, send audio wave data, switch back to AT mode.

RS232 level converters may be required, and you will probably need to use other GPIO, with level converters for hardware handshake (RTS etc).

USB is certainly an option.

As FLYFISH TECHNOLOGIES posted earlier, see Asterisk

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FLYFISH TECHNOLOGIES
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Re: Answer a landline

Sat Feb 15, 2014 12:45 pm

Hi,

I see here listed some modem models which could be used... but I'd like to point out (again) that a "landline" or "telephone line" don't describe what technology it is about. For example, "good old" analog line and ISDN are both phone lines, but modem for one line is not compatible with another line type.
Pay attention, it will help you to keep the magic smoke inside elements.


Best wishes, Ivan Zilic.
Running out of GPIO pins and/or need to read analog values?
Solution: http://www.flyfish-tech.com/FF32

ScottyDoesKnow
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Re: Answer a landline

Mon Feb 17, 2014 2:57 am

Thanks everyone for the quick responses. Luckily I haven't fried my raspberry pi.

In regards to legality, I don't even have an outside phone line (or even a dial tone). But the buzzer does come through. I may look up more info on this but I'm not too worried.

In regards to landline technology, I would assume it's just analog? I have no real clue though, is there any way I can check?

For modems, I've found a couple cheap ones that do include the word 'voice' at least. One says it will work on MAC OS X, but not sure whether that means it may work on the pi. To be honest I don't know if I want to spend $50+ on a modem for this project. Here's the ones I've found:

http://www.amazon.ca/USB-56K-External-D ... B0037ATHF4
http://www.amazon.ca/Sewell-Voice-Fax-M ... B005GQMX4O

Is it the case that the ones that will work are the ones that have an integrated DSP which is why they're all $50+?

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