My home came with a c.2007 On-Q Legrand Inquire 1000 intercom system. All stations only issue a gravely hiss. The Talk and Door buttons do not work. Mute works. Volume adjust works.

All units use Cat 5 cabling routed to a panel in a closet which is powered thru a power supply.

I am thinking I could install a Ring Doorbell Elite (or equivalent) using its PoE capabilities but it is quite expensive (after all is said and done ~ $500 per door).

I then wondered if I could just use the Cat 5 cable as a power cord (divide the wires into 3 sets for hot, common and ground) and connect it to a new transformer in the closet cabinet, then plug that into a wall socket. If so, that would cost me ~ $100 for the door bell, chime, and transformer.

I am at the idea/design stage so all suggestions that can utilize the Cat 5 cable to get me a door bell without having to pull new electrical cable or necessarily use WiFi would be appreciated.

  • \$\begingroup\$ Please DO NOT put mains voltage to a standard CAT5 cable please. Be aware that you should not put more voltage and current on such cable like POE does. Do you have 120 V AC or even 240 V AC? \$\endgroup\$
    – datenheim
    Commented Mar 24, 2023 at 19:10
  • \$\begingroup\$ OK, thanks for the caution. I was thinking I might be able to construct a simpler version of the Ring Doorbell Elite without it being tied to wifi - just enough voltage and current to run a simple door bell & chime using the POE injector concepts. Just a brainstorming idea. Sounds like it might be unsound... \$\endgroup\$ Commented Mar 24, 2023 at 19:31

1 Answer 1


Warning: Do never transmit 120V AC or 240V AC mains power over CAT5 cables (and also not CAT6 and so on). Their insulation is not up for that - it can result in smoke, fire and death.

But you may use a AC/DC converter (or transformer) and then transmit the low-voltage side over the CAT 5 cable for sure.

If you take 3 wires for + and for - you may transfer 1.5 A @ 12...48V without getting into trouble. That is enough for a lot of stuff. Having a fuse or current limiter might be a good idea ;-)

You still have 2 wires for signals...

Please refer to the answers here for more details: Voltage Drop and Safe Current Load on CAT5 Cable

  • \$\begingroup\$ Thank-you for your responses. I will follow your advise and see how it turns out. \$\endgroup\$ Commented Apr 13, 2023 at 0:30

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