Parallel phone connections and two modems attached to them

[kumarkumar]

I have parallel phone connections in all my rooms. I have a DSL broadband connection.

I have connected a modem in one room to which I connect one of my computer via Ethernet cable. It works fine.

I have another computer in another room and wish to connect it to internet as well. Now, pulling a long Ethernet cable from the above modem across rooms to the second computer would not be feasible.

I have another identical spare modem. So I thought I might connect it similar to the first one to the parallel phone outlet in the second room.

But as soon as I connect it to the parallel phone outlet in the second room the internet connection gets screwed up.

Is it not possible this way? If yes, why?

Edited September 11, 2011 by kumarkumar

[allen2]

Right now dsl modem doesn't allow this kind of thing (you only put one modem on one phone line) just like with any RTC modem. Perhaps in the future, there will be modem allowing this but i don't think so.

But you could perhaps use the parallel phone cable (usually with rj11 connectors) to transmit the ethernet signal although the other phone lines can't be used as phone lines anymore after this mods:

- Check how many wires are connected between two phones plugs (not only the connected wires, sometime there are more wires that are not connected and even in some cases ethernet cable was used to connect phones plugs). If there are less than 4 wires, then this is simply impossible as the lowest ethernet signal need at least 4 wires. If there are at least 4 wires (8 would be best to have at least 100Mb/s), you can continue to the next step.

- Identify where the phone line is first connected : usually, there is one phone plug which is connected to the external phone line and the at least on of the other phone plug. This phone plug will be called the "master".

- Now you need to disconnect the wires between the phone plugs except the external phone line which will stay connected to the "master" phone plug.

- Then if you had more than one phone plug connected to the "master", you'll need at least a ethernet hub/switch, if you wish to share internet between all connected rooms.

- Then you need to add a new female ethernet connector next to the "master" phone plug and wire it to the disconnected one (if you had more than one on the "master" plug, you'll need to add more ethernet connector as you need one for each). To wire it properly, read how there.

- Then do the same for each of the other plugs.

- then connect ethernet cable (cross over or straight depending on your modem and how you will connect all things).

As sometimes a picture is easier to understand here is an example : original phone wiring and after modifying it :

The black lines are the walls, the blue one are the existing cable between the phone plugs, red rectangles are the phone plugs, the green line is the external phone line and the brown rectangles are the ethernet plugs.

As you can see, the room 3 isn't connected directly to internet (you'll need to add either an ethernet cable or a hub/switch between the 2 ethernet plugs in room 2 if you want to use internet sometime in room 2).

[jaclaz]

If I may, if there is a "main" PC and a less used one, easiest would be to buy a couple network-over-power-lines adapters, principles:

http://computer.howstuffworks.com/power-network.htm

Examples:

http://www.newegg.com/Store/SubCategory.aspx?SubCategory=294&name=Powerline-Networking

If you can live with a slightly slower network, two of these (example):

http://www.newegg.com/Product/Product.aspx?Item=N82E16833122259

may fit the bill, if you want a speed comparable to an ordinary 100 Mbit lan, this (other example):

http://www.newegg.com/Product/Product.aspx?Item=N82E16833146001

should do within a still reasonable price.

(and you get anyway two hubs that ay come handy to connect a NAS or a notebook)

jaclaz

[bphlpt]

Another option would be installing a wireless access point and a wireless adapter for your other PC, if it doesn't have one already. Then comparing the cost of all the options mentioned so far, you might decide that pulling a long Ethernet cable might be "feasible" after all. (Cable is cheap after all.)

Cheers and Regards

[kumarkumar]

Right now dsl modem doesn't allow this kind of thing (you only put one modem on one phone line) just like with any RTC modem. Perhaps in the future, there will be modem allowing this but i don't think so.

But you could perhaps use the parallel phone cable (usually with rj11 connectors) to transmit the ethernet signal although the other phone lines can't be used as phone lines anymore after this mods:

- Check how many wires are connected between two phones plugs (not only the connected wires, sometime there are more wires that are not connected and even in some cases ethernet cable was used to connect phones plugs). If there are less than 4 wires, then this is simply impossible as the lowest ethernet signal need at least 4 wires. If there are at least 4 wires (8 would be best to have at least 100Mb/s), you can continue to the next step.

- Identify where the phone line is first connected : usually, there is one phone plug which is connected to the external phone line and the at least on of the other phone plug. This phone plug will be called the "master".

- Now you need to disconnect the wires between the phone plugs except the external phone line which will stay connected to the "master" phone plug.

- Then if you had more than one phone plug connected to the "master", you'll need at least a ethernet hub/switch, if you wish to share internet between all connected rooms.

- Then you need to add a new female ethernet connector next to the "master" phone plug and wire it to the disconnected one (if you had more than one on the "master" plug, you'll need to add more ethernet connector as you need one for each). To wire it properly, read how there.

- Then do the same for each of the other plugs.

- then connect ethernet cable (cross over or straight depending on your modem and how you will connect all things).

As sometimes a picture is easier to understand here is an example : original phone wiring and after modifying it :

The black lines are the walls, the blue one are the existing cable between the phone plugs, red rectangles are the phone plugs, the green line is the external phone line and the brown rectangles are the ethernet plugs.

As you can see, the room 3 isn't connected directly to internet (you'll need to add either an ethernet cable or a hub/switch between the 2 ethernet plugs in room 2 if you want to use internet sometime in room 2).

Thanks a lot for the detailed writeup and the pictures that you made. Really appreciate it.

I opened up the phone socket and had a look at the cable. Thankfully it has four wires (brown, blue, white, white). Thankfully I also happen to have a spare ethernet switch

Now I will have to purchase a RJ45 Receptacle and try this out.

Will get back to you on this.

You mentioned that I can get 100Mbps with 8 wires, what speeds can I expect with 4 wires?

[kumarkumar]

If I may, if there is a "main" PC and a less used one, easiest would be to buy a couple network-over-power-lines adapters, principles:

http://computer.howstuffworks.com/power-network.htm

Examples:

http://www.newegg.com/Store/SubCategory.aspx?SubCategory=294&name=Powerline-Networking

If you can live with a slightly slower network, two of these (example):

http://www.newegg.com/Product/Product.aspx?Item=N82E16833122259

may fit the bill, if you want a speed comparable to an ordinary 100 Mbit lan, this (other example):

http://www.newegg.com/Product/Product.aspx?Item=N82E16833146001

should do within a still reasonable price.

(and you get anyway two hubs that ay come handy to connect a NAS or a notebook)

jaclaz

Thanks a lot for the links. Nice to know about these devices being into existence.

I live in a country, where these are not available or cannot be procured. The only option would be to import them at exorbitant costs.

Hence, though would have loved these plug & play devices, its out of reach for me.

[kumarkumar]

Another option would be installing a wireless access point and a wireless adapter for your other PC, if it doesn't have one already. Then comparing the cost of all the options mentioned so far, you might decide that pulling a long Ethernet cable might be "feasible" after all. (Cable is cheap after all.)

Cheers and Regards

Its not about the cost involved due to long lengths, but the non feasibility lies in not being able to take the wire from one room to the other across gaps on walls, doors, windows, etc, leave apart it looking ugly.

[jaclaz]

You mentioned that I can get 100Mbps with 8 wires, what speeds can I expect with 4 wires?

You don't really *need* 8 wires, it is the kind of cable that makes a (big) difference.

The "normal" CAT 5 cable has 4 twisted pairs.

Of these ONLY 2 pairs are needed for 100 Mb networking (all four pairs are needed for 1 Gb one).

In a CAT 5 cable each twisted pair is twisted with a different space between twists (to reduce "cross talk"):

http://en.wikipedia.org/wiki/Category_5_cable

The good news are that this particular cable is intended for "professional use", with *any* length, to be crammed together with (say) another 15 cables in a small duct, etc. etc.

So it is possible that given the small legth of the cable you have, the fact that it is "alone", IF the "telephone cable" is of a "good quality" and a number of other factors, you may get the full 100 Mbit speed.

Problem might be the reliability of this connection.

Since there are no "intermediate" speeds, IF your cabling has problems (lost/corrupted packets) at 100 Mbit, you will need to "step down" to 10 Mbit.

Most probably IF there are problems they will be "intermittent" in the sense that "now it works", someone powers a vacuum cleaner or a neon light in the room and suddenly it won't work reliably anymore.

Depending on the uses you want to do (as an example to check e-mail 10 Mbit is good enough, to transfer files far less so) you may live with the lower speed allright.

Use this as a reference to see which actual wires are needed (pins 1,2,3,6):

http://www.nullmodem.com/RJ-45.htm

jaclaz

Edited September 12, 2011 by jaclaz

[kumarkumar]

I then have a weird cable though it looks like Cat5.

It has blue, brown, white, white (2 pairs) and they don't seem to be twisted

How do I manage with two white?

[jaclaz]

I then have a weird cable though it looks like Cat5.

It has blue, brown, white, white (2 pairs) and they don't seem to be twisted

How do I manage with two white?

You need:

• anything that works with a 9 V battery
  
• a couple pieces of wire (maybe even not needed)
  

You connect in one room one of the Whites with the Blue wire.

You remove partially the battery from the device, leaving only one contact clipped.

You go in the other room and connect the "free" battery contact to Blue and and the "free" device contact to the White (NO! not that White, the other one! )

When the device powers up you know you have found the "right" white wire, and you apply to it (in both rooms) a sticker with "I seem white but I am actually red at heart!" or "Pretend I am red!" to identify it.

Of course if you have a multimeter it is even easier.

jaclaz

Edited September 12, 2011 by jaclaz

[kumarkumar]

Thanks a lot jaclaz.

Very nice & simple idea. Should have thought about it. I feel stupid now.

I have a multimeter and now know what to do.

About the connections to the RJ45 receptacle, should I go with 10baseT Straight Cable (PC to HUB/SWITCH) or 100base-T Straight Cable (PC to HUB/SWITCH)? I am asking this because of the note mentioned in 10baseT Straight Cable.

[jaclaz]

Pinout is the same for 10base-T or 100base-T, as said the speed depends on the actual cable and what interferences it may get (internal or external).

The note is of the kind:

"Since you are going to make a cable and you have anyway a 4 pairs cable, instead of leaving 2 pairs not connected, connect them so that this cable will be useful for 100baseT, having the additional pairs in the right place".

Only pins 1,2,3 and 6 are used anyway in BOTH 10BaseT and 100BaseT and the pins 4,5,7 and 8 can be used for other things like POE, or for telephony, see the actual note for 100BaseT and linked to FAQ/article:

http://www.zytrax.com/tech/layer_1/cables/cables_faq.htm#q16

http://www.zytrax.com/tech/layer_1/cables/mixed.html

So, forget everything else, use this (already given as reference):

http://www.nullmodem.com/RJ-45.htm

You have:

• White
  
• Blue
  
• White Red
  
• Brown
  

You will break colour coding anyway, so simply:

• White -> Pretend this is white/orange and connect it to pin 1
  
• Blue -> Pretend this is orange and connect it to pin 2
  
• White Red -> Pretend this is white/green and connect it to pin 3
  
• Brown -> Pretend this is green and connect it to pin 6
  

jaclaz

[kumarkumar]

Thanks a lot jaclaz for the details.

Will go to purchase a RJ-45 receptacle that fits into the current electrical board this weekend and let you know how it goes.

[kumarkumar]

Is there a way to figure out which is the master phone socket? Using multimeter or whatever.

I live in an apartment complex and the wiring is concealed. I cannot figure out from where the external phone line comes in the house and then goes to which phone socket first and then to which and so on.

There are three phone sockets and the last one in the series is known (figured out by obvious reasoning). So remaining are two, one of which is the master and the other one in between. I need to figure out which one is what among these two.

[jaclaz]

Is there a way to figure out which is the master phone socket? Using multimeter or whatever.

I live in an apartment complex and the wiring is concealed. I cannot figure out from where the external phone line comes in the house and then goes to which phone socket first and then to which and so on.

There are three phone sockets and the last one in the series is known (figured out by obvious reasoning). So remaining are two, one of which is the master and the other one in between. I need to figure out which one is what among these two.

Sure.

But you need to disconnect the wires.

You are in a situation like:

----*-----

----*-----

Where the left side lines or dot are (for the sake of the example) the phone line coming in and the right side ones are the line going to a "next" phone socket (the * being the actual "first" phone socket)

You have to disconnect the wires on one side of the socket, like:

----* ----

----* -----

and measure with a multimeter the Voltage on botth the wires still connected to the socket and on the the ones that were disconnected.

Use ~ (Alternate Current) and a relatively HIGH Voltage setting on the multimeter, it depend on countries and standard (and actual REN number and what not) but a common telephone line may well be at around 48 V and when ringing well above 100 V.

jaclaz