Plug a landline into a 3G cellphone?

August 25, 2009 10:39 AM

retrofitting 3G networks back down to landlines: My cellphone has a 1.75mm jack for plugging in earbud/wires. Is there RADIO SHACK technology that can let me somehow plug a "landline" into a cellphone? Is there a secret cellphone code that can generate a "dial tone"?
posted by shipbreaker to technology (24 answers total)

Yes, but no dial tone. That's just silly. You'll need a 2.5mm -> 1.75mm converter, which I'm sure the Shack would love to sell you.
posted by fatllama at 10:42 AM on August 25, 2009

Not what you want, but SparkFun have a cell-phone or bluetooth module mounted in a rotary phone for Great Justice.
posted by fatllama at 10:49 AM on August 25, 2009

Perhaps what I do have is the 2.5mm. I dunno, someone told me it was a 1.75... ...
posted by shipbreaker at 10:49 AM on August 25, 2009

WHILE I'M DREAMING and people are listening to my dream...

I dream of connecting my AT&T Trimline 210 to my cellphone somehow, picking up the Trimline handset and getting a dial tone (or equivalent) from the cellphone.

I ought just buy an iPhone but that costs $$$ $$$ and my Trimline phone is only $5.
posted by shipbreaker at 10:52 AM on August 25, 2009

The dial tone is something generated by the phone company to tell the phone user that the phone is operational and ready to accept digits. In cell phones you type in the digits and then press send to send them. There's no connection prior, thus no rational reason for any kind of tone. I guess you can pay some developer to write you an app that will do this, but you;ll need to upgrade to a smartphone and run that app 24/7.
posted by damn dirty ape at 10:58 AM on August 25, 2009

Sounds possible only if you are willing to build a little circuit that features a generated dial tone (digitally via an audrino or something, or analog), and an analog switch that would detect the handset pickup and feed the dial tone to the handset, and would automatically switch over to the cell phone jack when it engages the call.

Sounds like another great project I'll never have enough spare time to do!
posted by fatllama at 10:59 AM on August 25, 2009

I have "Motorola Phone Tools" and it lets me connect a Motorola RAZR v3 to the computer, and send text messages. There's also a huge juicy button called "Internet" which supposedly establishes a PPP connection over the 3G network? but I cannot make it work, because my phone is a Pay-as-you-Go, not a contract phone. So I am wondering if/how I could connect my computer's analog modem to the cellphone via that 2.5mm earbud jack.

!!!
posted by shipbreaker at 11:00 AM on August 25, 2009

I'm doing my research now; it seems that what I want to do is called "tethering":

http://ask.metafilter.com/109325/Best-options-for-unlimited-data-with-pay-as-you-go
posted by shipbreaker at 11:04 AM on August 25, 2009

No. This is bound to fail. Sorry.
posted by fatllama at 11:05 AM on August 25, 2009

You cant use a regular modem over a cell connection.

You can pay for data tethering or if you phone doesnt support it, an older form of tethering called CSD.
posted by damn dirty ape at 11:08 AM on August 25, 2009

My real question is "AT&T Pay-As-You-Go Data Tethering?", sounds like "No" is the answer, and I should close this Q, but I will leave it open in case it catches on fire with cool answers!
posted by shipbreaker at 11:11 AM on August 25, 2009

Tethering is indeed what you want, but it will in no way involve your computer's modem. It is not a question of getting A to plug into B... there are latency and signal quality issues that make audio cell phone connections unsuitable for modems.... even though the underlying signal might be digital! Instead, a serial (or USB) cable will plug many cell phones into your computer, and an appropriate driver will treat the cell phone as the modem. But you need the correct cell phone service for that, probably through a contract, as you suspect.

And here I thought you wanted the sheer novelty of a dial tone coming out of a big handset plugged into a cell phone... which, btw, is way cooler than a wireless internet connection to a PC. But I reserve judgment.
posted by fatllama at 11:22 AM on August 25, 2009

Tethering for Internet access, but you started out asking how to use your old wireline phone with your cell phone.

There are bluetooth to RJ-11 adapters that sound like they do what you want, but they aren't cheap.
posted by Good Brain at 11:54 AM on August 25, 2009

I may be way off from what you are asking, but I know radioshack used to advertise something similar to the two things I'm about to link (I believe the product was meant to take advantage of cheaper cell long distance rates). Item 1, Item 2
posted by syntheticfaith at 12:12 PM on August 25, 2009

Just to expand a little on damn dirty ape, it used to be possible to plug an analog modem (or fax machine!) into a cellphone, with the appropriate cable, and connect to your ISP or dial another modem. This required "CSD" or circuit switched data service. Most cell carriers no longer offer it—I spent a lot of time talking to T-Mobile a few years ago about it, because I wanted to send faxes using a real fax machine plugged into a cell phone. They still offered it as a legacy service, but could no longer enable it for anyone new. Verizon apparently offers it for corporate customers, but good luck finding someone who knows how to set it up.

CSD works very differently from modern cell-data service, which operates up on the transport layer of the networking model and passes IP packets without ever dialing a phone number or interfacing with the POTS. This is what you want for 99% of data applications today anyway; you don't want to horse around with a modem, you want to connect your computer directly via Bluetooth or USB (this is what the Motorola PhoneTools package does) and talk TCP/IP. (Or at least PPP; in some instances Windows does a PPP-over-Bluetooth thing, and sometimes it uses a newer BT profile that actually passes packets directly.)

So to get to your question regarding modern data service on a PAYGO phone, ATT used to have a pretty nice one—so nice, they axed it. Now, the only data plans available without a contract are 1MB/mo (that's right, one measly megabyte) for $4.99 and 100MB for $19.99. It's possible they have some 'secret' plans or deals available if you call them, but I doubt it. They seem to be pushing people who want data onto contract plans really hard.

I think T-Mobile might have a plan that would allow this, though, if you're willing to move your number over. The basic plan you'd want is one of the "FlexPay" ones (which are PAYGO, but not prepaid—they're the "no contract" plans) and then you'd want to add an unlimited-internet package to it. I think based on some forum postings that you'd need to buy a $25 or $30/mo internet plan, not one of the $10 or $20 cheapies—those only work in conjunction with certain high-priced voice plans.

Sometimes when I've called up TMO they've actually given me unadvertised specials, so I wouldn't trust their website completely.
posted by Kadin2048 at 12:24 PM on August 25, 2009

You can use a regular modem over a cell connection, but it will only work at speeds so slow that a PPP connection will be difficult to establish (ie, <9>this as long as you have a compatible phone. As Good Brain said, not a cheap solution.

As for tethering, AT&T will not let you tether a Pay as You Go phone. They do have tethering plans for monthly contract subscribers, which are typically used with Blackberries and Windows Mobile smartphones; these plans are rarely less than $80/month or so just for data charges -- they are not a cost-effective replacement for a basic landline. With tethering, you would connect your computer to your phone to your computer via USB or wirelessly via Bluetooth to establish the connection.

posted by eschatfische at 12:27 PM on August 25, 2009

My last comment got munged by the use of the less than operator. Here it is again:

You can use a regular modem over a cell connection, but it will only work at speeds so slow that a PPP connection will be difficult to establish (ie, less than 9600bps). You could almost certainly establish a 1200bps connection to a text-based service, however.

That said, your dream of connecting your AT&T Trimline or analog modem to your phone is possible with a device such as this as long as you have a compatible phone. As Good Brain said, not a cheap solution.

As for tethering, AT&T will not let you tether a Pay as You Go phone. They do have tethering plans for monthly contract subscribers, which are typically used with Blackberries and Windows Mobile smartphones; these plans are rarely less than $80/month or so just for data charges -- they are not a cost-effective replacement for a basic landline. With tethering, you would connect your computer to your phone to your computer via USB or wirelessly via Bluetooth to establish the connection.
posted by eschatfische at 12:27 PM on August 25, 2009

Technical correction to above: modern cell-data systems like GPRS/EDGE are probably best described as being on OSI layer 2 ("data link" layer services), and they carry layer 3 ("network" layer) services, IP in particular, across themselves. The transport layer is built on top of that, but it's probably wrong to call it a 'transport layer' service.

At any rate, they operate several layers of abstraction higher than older systems like CSD, which is more like ISDN. I probably should have just said that and shut my mouth.

/nerdery
posted by Kadin2048 at 12:31 PM on August 25, 2009

Interoperability is not feasible. For all sorts of electrical signal incompatibility reasons. But don't give up. It is this dream that Google Voice was created to fulfill. Your new problem is how to get an invitation ... :-)
posted by Susurration at 12:45 PM on August 25, 2009

There are actually desktop phones that take SIM cards, meaning if you have a phone from the AT&T or T-Mobile networks you could pop out the card (usually located next to the battery) and put it in your desktop phone at home. Here's a Google Product Search (I wish it was still Froogle) for the device. They're kinda expensive, though, and really meant for offices in places that can't manage to get a dedicated phoneline.

Granted, this isn't as simple as just plugging the phone into something, but you will get the old-fashioned telephony experience.

ahem

Reading further, I see you're into tethering. This is a pretty backwards way to go about it. What you'll want is to get a prepaid plan that has data, and a phone that supports tethering either out of the box or via third party hack. I've done it on my Samsung Sync A707 on AT&T through OSX's bluetooth networking tab. With enough Googling, I'm sure you could figure out how to do it with a cheap handset from Google, the right plan, and your OS.

Dial-up, though, is the wrong way to do this. The clarity and latency of a cellphone line means that getting a connection will be hard, and that the connection you'll get will be pretty dismal both in terms of uptime and speed. You'd be much better off just buying a standalone mobile data plan and PC card 3G modem, or a paid Wifi plan if you live in a fairly urban area.
posted by mccarty.tim at 1:10 PM on August 25, 2009

Try the Dock-N-Talk
posted by miyabo at 4:32 PM on August 25, 2009

Or the CellSocket or XLink

Not Radio Shack, but I think they do what you want
posted by miyabo at 4:39 PM on August 25, 2009

I'm loving the Google Search for "GSM desktop phone"... ... that gets me closer to the spirit of what I was looking for! As I mentioned, the MOTOROLA PHONE TOOLS that came with the Motorola Razr V3 has a huge button called "INTERNET" which teases me with the potential to create a PPP connection on my computer, but my Pay-As-You-Go service won't let me do a data connection that way! Looks like (a) buy a landline and get DSL/dialup or (b) get a contract phone with a Data plan -- are my two options so far.

Don't they make "G3 wireless PC modem" cards by now?
posted by shipbreaker at 9:54 PM on August 26, 2009

yes, they make 3g wireless cards and USB dongles by now.
posted by Good Brain at 10:05 PM on August 26, 2009