Trying to hook phone hybrid to digital line

[RichPowers]

Maybe someone can help me with this.

To start with, I am getting conflicting information on if cellphones are digital or analog..

Maybe someone can help me with this.

To start with, I am getting conflicting information on if cellphones are digital or analog..
I would prefer to use a cellphone for call-in talk programing, to avoid having to pay for an additional business line rate (as this location is a business address).

I’ll be using a “Phone-Jam” telephone hybrid unit for call-ins (phone-jam.com). These aren’t manufactured anymore and support isn’t available, but in their FAQs they say:
Q: Can you use the PJ with digital telephones or phone lines?
A: Yes. As explained briefly earlier, you can use a digital converter *(which is NOT included with the PJ) to hook into a digital telephone line or phone system. We have found that KONEXX connectors work the best with our system.

Well, I found this Konexx adapter http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557
But the only information I can find about them say nothing more than: Konexx Konference 1QVUSA-23752-KX-N Connects Analog Conference Unit To Virtually Any Digital Phone System Adaptor”
and it just doesn’t clarify it enough to me if this is the correct item I need.

Other searches emphasizes never to connect an analog phone or system to a digital line because it could fry something.. so I want to be sure about what I need to get.

Any kind of digital/analog adapter I find are rather expensive.

So to sum it up..
1.I prefer to use a cell-phone connected to my hybrid for on-air call-ins. — or if not use Comcast’s digital land land.

2.My hybrid can only be connected to a digital line with an adapter, but I’m confused on what kind of adapter, and am also hoping for cheaper alternative, if I can’t the proper one used for cheap.

Any suggestions or ideas please

[Carl Blare]

This question is over my head, but it is a good chance to discuss what little is known about telephone technology.

Basically, all audio transmission begins and ends with analog, since speech is inherently analog, and human hearing is analog. Therefore the “front-end” of all telephones start with analog, and at the “end-end” all audio transmissions come out in analog.

The in-between transmission is a whole other question.

An ordinary POTS (plain-old-telephone-subscriber) line is analog tuned for about 300 to 3,000Hz, but a second phone line can be piggy-backed by applying a high frequency (analog) radio signal at about 10kHz which is AM modulated (analog) with an audio signal, and later demodulated back to base-band audio.

Even though that’s all-analog, it still requires specialized handling to hear the “sub-carrier” signal.

Convert to digital and I’m gone. I do know that there are probably countless digital protocols, maybe some are proprietary. Is there such a thing as a specialist who understands the subject in a general way?

[dosman]

First, you aren’t going to be able to use the Phone-Jam with a cell phone without some trickery. You have to provide a POTS/analog dial-tone to the Phone-Jam, there’s really no way you can do this from a cell phone without building some complicated circuitry. As far as using a digital line, I’m not clear on what you are trying to do. If you are using the Phone-Jam on a digital line, then yes a digital phone adapter should work ok. Like you’ve read, directly connecting the Phone-Jam to a digital line would be very bad, as long as there is a digital adapter being used though it should be ok. However, connecting a cell phone to the Phone-Jam is a completely different subject than connecting it to a digital phone system.

You MAY be able to wire the cell phones mic and headphone to your playout system’s mic input. The easiest way is to use a cell phone with a phono jack/headset connector. Then make yourself a headset-to-computer cable. Generally a headset plug will be a stereo phono connector with the mic on one channel and the output on the other channel. Usually a phone has both sides of the conversation on the speaker, so all you need is to wire the speaker to the mic input on your computer. You will have to experiment a little, but it shouldn’t be too hard to setup. External mic into the phone, phone output into the mic of the playout system.

Another alternative if you really want to use the Phone-Jam is to setup an Asterisk PBX on a Linux system. Again, this isn’t trivial, but with an Asterisk PBX card you could provide a real POTS dial-tone to the Phone-Jam (and have real phone connectivity via a VoIP provider or interfacing to your digital phone system). This should only put you back ~$200 to build a complete system on the cheap.

Hope that helps some.

[Author]

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