Why is there a phone line plugged into my modem?

chrstrbrts

Senior member
Aug 12, 2014
522
3
81
Hi,

I get internet, phone, and TV all through what used to be just a cable TV provider. (They converted into a general data provider years ago just like everyone else.)

Anyway, there's a coax cable coming from the street through a wall in my house and into a modem.

There also is a regular phone line coming from the street into the same modem.

What is the purpose of the regular phone line?
 

Gryz

Golden Member
Aug 28, 2010
1,551
204
106
None.

It could be of OOB management. (OOB = Out of Band). OOB means there is a separate way to get into a device, besides using the network of which the device is a part. OOB management is helpful when the network is messed up. Suppose they configure the wrong ip-address on the outgoing network port of your modem ? They can then not reach your modem anymore. But with OOB management, they have a way to get into the modem and correct or reset the config.
This happens for important (and remote) network devices. I never heard providers do this for subscribers (regular home users).

May I suggest you just call your provider's helpdesk and just ask ?
I bet they give you an honest answer.
I'm curious now.
 

boomerang

Lifer
Jun 19, 2000
18,883
641
126
Are you certain that phone line is coming directly from outside? Disconnect it at the modem and see if your house phone(s) work. I'll bet you don't get a dial tone.
 

Thebobo

Lifer
Jun 19, 2006
18,574
7,671
136
Is there a label on the modem where this line plugs in?

Pics off modem and line?
 

vailr

Diamond Member
Oct 9, 1999
5,365
54
91
There also is a regular phone line coming from the street into the same modem.

The more likely circuit diagram would be: coax cable coming in from the "street" to the cable modem, then a telephone line connection from the cable modem to the whole house telephone circuitry. That's assuming that you have "land line" telephone service set up via your cable company, and not via P.O.T.S. (plain old telephone service). Check your cable modem model number online, which it should show up as a VOIP cable modem.
 

Ichinisan

Lifer
Oct 9, 2002
28,298
1,235
136
It's probably just a network cable for getting a wired internet connection from the modem.
 

ch33zw1z

Lifer
Nov 4, 2004
38,337
18,871
146
Who's your provider and what's the modem model, pics would help.

Long ago, some cable modem providers only offered downstream via broadband, upload was over 56k, hope that isn't what you have lol
 

Ichinisan

Lifer
Oct 9, 2002
28,298
1,235
136
Who's your provider and what's the modem model, pics would help.

Long ago, some cable modem providers only offered downstream via broadband, upload was over 56k, hope that isn't what you have lol
I had that setup back in 1999. There was a "COM21" brand modem that probably wasn't DOCSIS compliant. Dial-up was done using the modem on my computer. There was no phone line jack on the modem; only a 10-baseT Ethernet network jack.