Question on taking audio from a phone line

I am in the process of getting a podcast together and it would involve taking audio from the phone lines. My audio isn't as important because I can record it just fine in my studio. I mainly want the callers audio to be good from their end.
 
Some podcasts will do a co host show and the person who isn't in the studio will drop box a better recording to the studio. If they use Skype they might use it to line up the two audio tracks. I won't be doing this because I don't have a co host and because I don't want to require my interviewees to email me audio every time I talk to them.
 
I know people use Skype or the Google equivalent but basically most serious podcasters seem to use something like a Zoom recorder to record the audio and then they upload from SD card to computer and work with the audio. This eliminates all of the issues involved with lag time, computer noise and the unexpected computer glitch. I think it makes sens,avoids voip all together and keeps everything to a simplistic minimum. When using a zoom to record they also use a mixer to put one channel back through so the listener can hear the other person.
 
I know there are expensive specialty items for this but I don't want to spend ton of money on this and most of those won't work because they deal with an old analog phone line and I have my phone through my cable company. The cable company has a modem with a phone jack on it and I don't believe it works in the same way or would work with many of those other options.Plus I use cordless phones.
 
Here is an idea I had and I am open to comments or suggestions.
 
I get a phone system with multiple handsets from the same base . These handsets are capable of using a plug in headset. I take one handset and use that as my phone while also recording on my studio mic. I take another handset and use that as the phone to output the other persons audio. The only part of the output jack I would use from that handset is the audio out from the caller. I dial the show guest and soon after connection is made I put the second handset online and put that audio into my Mackie mixer to boost the signal and then forward it into a zoom recorder on one channel. I also take my audio into the same mixer and run it into the second channel of the zoom. 
 
I looked at the output jack on the phone handset I have and it is smaller than the typical 3.5mm found on most cell phones. I'm not sure about the impedences. I can get an adapter to take it from the smaller phone jack to a standard 3.5mm and I have a connector goes from 3.5mm to RCA L/R.  Any thoughts?
 

If you are talking landlines it is better to retrieve the signal from the phone line itself using the right gear though. You need a thing called a Hybrid. It essentially isolates the audio component and sends it out a separate output that can be used in studio and recording situations.
 
You can make one too as I did mine. It is bascialy a decent quality 600 ohm 1:1 transformer fed with a cap in series to remove the DC component on the phone line. The secondary winding can be used as the isolated output. Both conversations will appear on the audio line. (Yours (sidetone) and the other person that is)
 
As Mike says JkAudio seem to be in the business of providing such hardware.
 
The handset probably has a 2.5 mm connector on it. You could also start by trying a lead from that to 6.5mm jacks etc for the mixer end etc.. The signal might be OK there as well.

Thanks guys for your suggestions! 
 
Jeff, using the "right gear"  as you say is what I really wanted to do in the beginning and it's what I knew I should do. Since I already had the phone I figured maybe I could make use of it effectively. I think my idea for using it probably would have worked in the way I described but that whole thing would have been a band aid approach to the problem. I also checked out some of the JK gear Mike mentioned and it isn't terribly expensive.
 
I could  build something simple for the purpose, you all had some good recommendations on that, but when I seen the thing wst3 mentioned...the Symetrics TI-101 and looked at it.....that looks like the kind of thing radio stations use. It looks well built and it has  lots of capabilities. I was afraid of the cost and went to eBay to check it out......long story short I seen a deal I couldn't pass up and it should be at my house in  few days! I appreciate the help in finding something.
 
The thing is....I'll be using this a  lot,so I don't want something flimsy. I'm very happy with this choice. My only concern is my phone system. I take my phone feed off of a cable modem and I think it has jacks for two phones. In theory at least, I should get the same thing at the jack that you would get from any analog phone jack, otherwise how could a  typical home phone either cordless or not be cross compatible? Unless something in the phone or modem recognizes a difference and makes an internal change. I can plug any kind of phone into that jack as far as I know. The fact that it went through a  D/A conversion process across my cable system shouldn't matter. I hope I'm right about this....if not I'll be reselling this item.

Thanks Jeff!

Starise
I take my phone feed off of a cable modem and I think it has jacks for two phones. In theory at least, I should get the same thing at the jack that you would get from any analog phone jack, otherwise how could a  typical home phone either cordless or not be cross compatible? Unless something in the phone or modem recognizes a difference and makes an internal change. I can plug any kind of phone into that jack as far as I know. 

Tim, the #2 jack is only active if you have a second phone line with a separate phone number.
You can use a simple dual outlet/splitter plugged into the #1 jack.
 
Yes, the phone jack is effectively just like a normal pots jack, even though the modem is using voip.
 
A good signal is critical for you, and phone/internet is particularly sensitive to signal issues.
If your cable provider is Charter, I can check it from here (I'm a Charter tech). If you are using Time Warner, have customer service test it. They can see the same thing I can in their own system.

It's normally 24v here in the US. The fact that the signal is carried over cable is not terribly relevant. The output of the phone jack mimics what a standard pots line would deliver.
It's funny you mention that, though. The phone company used to adjust "ringer equivalence" to compensate for multiple phones in a home. I don't know if that was accomplished by increasing voltage or amps. My guess is voltage, because phone lines are very small, maybe 22ga at best.
Not long ago, I had a customer who had seven old school phones. The cable modem could not provide enough power to make them all ring. He could talk on any of them.
At any rate, the modem output is 24v, very low amperage.

In the US the DC voltage on a plain old telephone service (POTS) line is 48VDC. When the telephone goes off hook it closes a switch which draws current from the central office, starting the whole process. In the really old days they would reverse the polarity of the DC voltage to create party lines.

The ringing voltage is between 80VAC and 90VAC, at 20 Hz, and the duty cycle was 2 seconds on, 4 seconds off. As a kid I was taught that ten rings took one minute... an odd way to time things!

Line voltages, and ringing voltages and cycles differ from country to country.

For the theatrical types - a ringing generator is easy to build, but lately I've used a 70V amplifier (an old Toa) and I drive it with audio files that I created to provide different ring cadences.

Keep in mind that when the TI-101 was a current product the rules concerning telephones and the telephone network were very different! The whole landscape was different! The cost to have a device "type accepted" for direct connection to the public telephone network was beyond that which could be amortized even if every broadcaster purchased one!

So companies skirted around the issue by printing in their manuals that the device can not be connected directly to the network, and the devices themselves were designed to be invisible to the network.
 
But that's not how people used them<G>!
 
I modified quite a few TI-101s to add a holding coil and a simple switch to the front panel. The switch places the coil across the tip and ring, and will draw dial tone, or accept an incoming call. With that in place you need only connect the TI-101 to a POTS line, or a reasonable facsimile thereof. As an added benefit, there is no transmit audio, so you don't need to disconnect the handset transmitter.
There were also a number of companies selling modified "type 500" subsets with "off-hook" and "xmit kill" switches built into the housing. The first switch simply sat in parallel with the hookswitch, and the second interrupted the transmit side of the handset. There might have been something else we had to do, but I do not remember the details any longer - you might check some of the broadcast engineering web sites for ideas if you want to try that.


Holler if you have questions...

Update- The setup seems to work fine without the unhook mod if I simply use my existing phone as the unhook device. I then need to make sure that phone isn't near the rest of my gear which isn't really a problem . I monitored through my  recorder. This way I can hear the actual signal as recorded. 
 
The TI-101 seems a bit noisy in monitoring, but the noise doesn't appear to be recorded to the degree I hear it when recording. Actually you don't hear the noise on the recording. I don't think this box was in a smoke free studio. The pots need lubed but I don't think this is going to solve the noise issue.Might have a leaky cap...or were these boxes that noisy? Seemed a bit excessive to me, even for older electronics.

Almost off topic. My Dad worked for BC Telephone for 40 years, (now known as Telus,) he explained that party line ringers where all 90 Volts, but each phone had a capacitor ( dumbed down explanation) that filtered out the cycles. Party one was 20 cycles, party 2 way 40 cycles etc.. I was just a kid, so memory might be off,,,well it's always off,, but... 
He was responsible for big office building networks in Vancouver,,, he retired when they started talking digital... he worked with 100's of pairs of colour coded wires.. 100% analog. His first job was a telegraph operator. 
 
http://www.cowboycountrymagazine.com/2011/03/fence-phones/