My father designed and built a large house about 10 years ago. Back then, internet was not 'popular' and so when it came to communication facility, he chose to install a PABX and ran all the wires inside wall, but didn't really use it.

Last year, we installed internet and wifi. The problem is that wifi can only cover a limited area, not the whole house. So right now, we have the telephone line from ISP, the wireless modem router, a PABX as pictured in the central room, and RJ45 outlet connections in every other room.

To get internet in every room, can I simply connect the wireless modem router to the PABX system - router outlet is RJ45 while PABX inlet is RJ11, should there be a problem?

Or do I have to connect the ISP telephone line to PABX system, then get a modem for each room? Connecting ISP line to PABX is fine (both RJ11) but outlet connection in each room is RJ45 while modem requires RJ11 inlet.

Or should I just get a wifi repeater, or a super strong wireless router? We want a setup that minimizes additional physical wirings, except from those wires already running inside the wall.

1 Answer 1


Find out what grade of cabling he ran to all those RJ45s. If it’s Cat5 or better, then use it as Ethernet. Install the broadband modem/router near the PBX (assuming the PBX is in a wiring panel/cabinet/closet near the patch panel where all the Cat5 cables terminate). Connect the router’s LAN ports to the Cat5 cables that run to jacks where you want to place additional Wi-Fi APs. If you want to use more jacks than your router has LAN ports, buy a cheap gigabit Ethernet switch and put it between a LAN port of the router and a bunch of Cat5 cables.

  • This setup means that I can throw the PBX away right, i.e. connecting the cables straight into router's LAN ports? Feb 2, 2017 at 8:07
  • What you do with the PBX depends on whether you still want landline telephone service or not. If everyone has mobile phones and you don't need a landline anymore, then sure, get rid of the PBX.
    – Spiff
    Feb 2, 2017 at 15:22
  • What if the cables are not Cat5? Can I use PBX to split the telephone signal, and then in each room, use a separate modem to convert it to internet through the DSL port? Feb 3, 2017 at 1:05
  • 1
    No, if the cables are just voice grade (Cat 3), there aren't many good options. You could do old 10Mbps 10BASE-T Ethernet over it, I suppose. A PBX isn't a signal splitter, it's an automated physical switch, that physically connects different phone line extensions together based on how the user dials the phone. It's very specific to landline telephone service, and doesn't do anything for DSL. You can't hook more than one DSL modem to the same phone line, no matter what. The DSLAM at the ISP has no way to handle multiple DSL modems on the same line.
    – Spiff
    Feb 3, 2017 at 1:21
  • Oh very well explained. I understand now. Many thanks. Feb 3, 2017 at 2:14

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