# cell phone through home phone

#### peter_w

Joined Dec 12, 2022
5
hello. i am wondering what is the simplest way to connect a cell phone to a old school home phone so the home phone rings when someone calls the cell phone and allows the home phone to make calls through the cell phone. i would like to build a circuit that can do this so i can use my old school phone this way for as cheap as possible. i would prefer a wired connection that somehow allows me to directly wire my home phone to my cell phone. you may wonder, whats the point? well, to be honest the light from the screens of "modern" technology bugs my eyes. i am even typing this while looking at an old crt computer monitor as i needed to switch for the same reason.

#### AnalogKid

Joined Aug 1, 2013
10,218
You used to be able to get a device to do this from some cell service providers. Maybe you still can, but it's been many years since I've seen an ad for this.

To your question - for a home builder/hpbbyist, there is no simple way. Everything about a cell phone, including both audio signals, signalling, ringing, answering (off-hook detection), etc. is done with packets of digital data - computers talking to computers. Everything about an "old-school home phone" (called POTS - Plain Old Telephone Service (yea, that is the real name)), is done with analog voltages. For an older cell phone with physical buttons, it is theoretically possible (but extremely tricky/difficult) to build a group of interfaces for the mic, speaker, the answer button, etc. That is essentially what a commercial device does. For a touch-screen phone, fuhget about it.

OR -as was posted while I was writing, you can do it through the Lightning / USB connector. Pretty sure this still would take a microprocessor to do all of the things listed in the ad, but I've not taken one apart to see.

ak

#### peter_w

Joined Dec 12, 2022
5
thanks for the thoghts. the cell2jack seems like it would work but i was hoping for a wired connection and to figure out how to do this for around 10 bucks cause im poor. i did learn since my post that there is such a thing as usb-c headphones for phone calls. im wondering now if i took a usb-c cell phone cord and stripped the wires and took a home phone cord and stripped the wires and connected the wires that connect to the wires where the headphoens would connect to via usb-c, if it might work, for both receiving and making phone calls. what do you guise think?

#### BobTPH

Joined Jun 5, 2013
6,294
Half of it can be done for $0. Forward incoming calls from the cellphone to the home phone. Di you really need the other half, making calls on your home phone go through the cell? #### AnalogKid Joined Aug 1, 2013 10,218 the cell2jack seems like it would work but i was hoping for a wired connection It is a wired connection. A standard hard-wired phone plugs into the device. They show a cordless phone in the images, but a plain old desk phone will work. i did learn since my post that there is such a thing as usb-c headphones for phone calls. im wondering now if i took a usb-c cell phone cord and stripped the wires and took a home phone cord and stripped the wires and connected the wires that connect to the wires where the headphoens would connect to via usb-c, if it might work, for both receiving and making phone calls. what do you guise think? No. A standard phone runs on a -48 Vdc compliant current source. The operating voltage drops down to around 8 Vdc when the phone is in use. The ring signal is a 90 V (-ish) 20 Hz sine wave. None of this is in any way compatible with USB signals, headset signals, etc. For the pedants out there: I stated values that are typical for US phone services. The actual voltages and currents for POTS varies around the world. Still, none of them are directly compatible with headsets, USB-anything, etc. ak #### Ya’akov Joined Jan 27, 2019 7,026 thanks for the thoghts. the cell2jack seems like it would work but i was hoping for a wired connection and to figure out how to do this for around 10 bucks cause im poor. i did learn since my post that there is such a thing as usb-c headphones for phone calls. im wondering now if i took a usb-c cell phone cord and stripped the wires and took a home phone cord and stripped the wires and connected the wires that connect to the wires where the headphoens would connect to via usb-c, if it might work, for both receiving and making phone calls. what do you guise think? No, that will not work. You could adapt a Bluetooth speaker that has a microphone, and they can be very cheap, but it won‘t be simple. #### ronsimpson Joined Oct 7, 2019 2,609 For years we used what looks like the item in #2. During those years an extra cell phone was only$10 but a land line was \$40.
We transferred the old land line number to the extra cell phone, which then would ring all the old phones in the house.
The old phones worked much like they did.
After two years, everyone had a personal number, and the house number was not important.

#### peter_w

Joined Dec 12, 2022
5
thanks for all the replies. i went out and bought a 50 cent pair of headphones from the thrift store in town. im going to strip one of the earbud wires and connect those two wires to the two wires that go to the home phone. im just going to see what happens. my thoughts are that the call/hang up button on earbuds might work the same with the button that ends calls on the home phone. since the home phone has buttons for dialing, i want to see if it will place calls in a similar way that those two bluetooth devices on here do. somehow the cell phone uses the home phone tech to make and receive calls with the bluetooth version, so maybe the headphone jack spliced version might work. i know the home phone needs only a tiny amount of power and im hoping the amount sent to the earbud will be enough. even if it doesnt work, it seems like there should be a cheap way to make a homemade version of those bluetooth devices that connect home phones to cell phones. i just dont know what the parts are to make that thing. i know id need a female rj11 connector and a 5 volt power supply and the piece that does the bluetoothing and would have to know how to connect the rj11 connector to the bluetooth thing. but since im not making this to sell, i could just wire the rj11 cord directly to the bluetooth component and hardwire the 5 volt power supply. i do have a soldering iron and solder. (lead free solder btw) seems most of this stuff i could find around the house or from a thrift store. i dont know what the bluetooth component is but maybe there is one inside a 50 cent thing at the thrift store or maybe it cost that much from a component site or amazon. im guessing there isnt many components to the bluetooth thing. i might be able to figure it out alone but would appreciate the help if you want to. i even want to switch to an old school am/fm portable radio too. like a walkmann or something. maybe that could be another post/project to build.

#### BobTPH

Joined Jun 5, 2013
6,294
Home phones work on about 48V. If you connect your earbud to a home phone line, it will likely result in a blown earbud.

#### peter_w

Joined Dec 12, 2022
5

#### peter_w

Joined Dec 12, 2022
5
i just came up with an idea that will probably work. instead of using the whole home phone, i might actually just use the part you hold to your head that has the one speaker and one microphone. this way, its technically the same as the one side of a pair of headphones that has the mic. instead of a on/off button for calls, i think it might work to just use google voice to make calls and texts right through the old school phone part that you hold to your head. i feel like from this experience i just got ads and hot air. thanks anyways

#### Ya’akov

Joined Jan 27, 2019
7,026
If all you want is a handset, here.

#### strantor

Joined Oct 3, 2010
6,383
i feel like from this experience i just got ads and hot air. thanks anyways
don't forget to tip!

#### dl324

Joined Mar 30, 2015
15,510
the cell2jack seems like it would work but i was hoping for a wired connection and to figure out how to do this for around 10 bucks cause im poor.
Is using a Bluetooth enabled computer an option? This is for Android phones:
Make and receive phone calls from your PC - Microsoft Support

You can also send and receive most text messages on your computer using Google's message app, but it requires a network connection.

You can do the similar with iPhones.

#### AnalogKid

Joined Aug 1, 2013
10,218
i just came up with an idea that will probably work. instead of using the whole home phone, i might actually just use the part you hold to your head that has the one speaker and one microphone. this way, its technically the same as the one side of a pair of headphones that has the mic. instead of a on/off button for calls, i think it might work to just use google voice to make calls and texts right through the old school phone part that you hold to your head. i feel like from this experience i just got ads and hot air. thanks anyways
That thing you hold in your hand is called a handset. Across manufacturers, the electrical characteristics of the earpiece can vary a lot. This means that one handset might be much louder than another. Most handsets today use an electret microphone cartridge that needs an external DC power source, Old handsets have a carbon microphone that needs much more current running through it.

If you know the characteristics that the device interface expects (pinout(s), voltages, impedances, etc.) and the characteristics of the mic and earpiece in the handset, we can advise on how to connect them and it an interface circuit might be needed.

gigo

ak

#### strantor

Joined Oct 3, 2010
6,383
Is using a Bluetooth enabled computer an option? This is for Android phones:
Make and receive phone calls from your PC - Microsoft Support

You can also send and receive most text messages on your computer using Google's message app, but it requires a network connection.

You can do the similar with iPhones.
That thing you hold in your hand is called a handset. Across manufacturers, the electrical characteristics of the earpiece can vary a lot. This means that one handset might be much louder than another. Most handsets today use an electret microphone cartridge that needs an external DC power source, Old handsets have a carbon microphone that needs much more current running through it.

If you know the characteristics that the device interface expects (pinout(s), voltages, impedances, etc.) and the characteristics of the mic and earpiece in the handset, we can advise on how to connect them and it an interface circuit might be needed.

gigo

ak
TS came in with a confused question, got relevant answers and discarded them, proposed his own harebrained solutions that my 8y/o would be able to identify as ridiculous, insulted everyone who helped him, and then stomped off. Your efforts are wasted; He can't be helped further even in the unlikely event he ever does come back and see your replies.

#### bassbindevil

Joined Jan 23, 2014
681
Since cellular reception was spotty where I lived, I kept my flipphone in one spot that got a signal and used a Bluetooth box from GE to link it to my cordless phone.