cat 5 connections

October 14, 2009 at 19:29:59
Specs: Windows XP
I just purchased a house where the previous owner ran cat 5 to all of the phone receptacles in the rooms. He left the phone wires attached to the jacks and the cat 5 is wound up inside the box.

I run off of VOIP telephone service. Should / can I connect all of the cat 5 and plug my telephones into the cat 5 receptacles?

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October 15, 2009 at 05:20:56
You could but you would have to change the plugs on the telephone. Cat5 cable usually terminates with an RJ45 socket to take an RJ45 plug.

Telephones cables terminate with an RJ11 plug. An RJ11 plug will fit into an RJ45 socket but it is slightly smaller and won't work correctly. RJ45 plugs have eight connections but only four are normally used for an Ethernet network. RJ11 only has four connections.


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October 15, 2009 at 07:47:24

Just FYI...

You can use an RJ-11 in an RJ-45 and have it work correctly. We've done it numerous times here where I work. If you use standard wiring (A or B) on the RJ-45 keystone, your middle two wires will be the blue pair. With an RJ-11 plugged into the socket, the blue pair will match up with the red/green pair of the phone wire once you've plugged the RJ-11 into the center of the RJ-45.

Then it's a matter of what the other end of that network cable connects to to make it all work.

We have some special BIX blocks that also have RJ-45 connectors which are very handy for changing over from a network connection to a phone.

Also, for 1000 Mbps, you use all 8 wires, it's only for 10/100 Mbps that you only use 4.


Yes you should be able to get RJ-45 "keystone" connectors and punch the Cat5 cable onto it.

You will however need to punch the other end of the cables either onto a patch panel (recommended) or onto RJ-45 connectors. Then, those will have to be plugged into a switch which connects to your internet so that you have internet access for the VoIP phones.

Typical setup would look as follows:

Highspeed Modem >> SOHO Router >> Switch >> Clients (PC's, VoIP phones etc)

Your patch panel should be near your SOHO router and switch (which ideally should also be very close together and connected with a crossover cable) so you can jumper from patch panel to switch.


When it comes to network cabling, you will want to test all cables once you're finished to make sure they work properly. Those cheap "blinking light" testers are useless. I would recommend calling a company that installs network cabling and asking them how much they would charge you to test/certify "X" number of cables. In fact, I would call around and get quotes from several and go with the best price.

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October 16, 2009 at 10:34:28
Curt R is absolutely correct.

MOS Master Certified
MCP Certified
CCNA Certificate Pending
A+ Certificate Pending

"I have gone to find myself. If I get back before I return, please tell myself to wait." :

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