I'm trying to use a cat5 network cable and connection jack (what I'm calling the female version of cat5) as a way to quickly connect/disconnect 8 wires for an electrical project. I bought a few cat5 cables and checked them for continuity and all the wires are intact. Then I bought an old D-Link router and unsoldered a cat5 jack from the board.
My issue is when I plug my cat5 cable into the separated jack and check the continuity from the other end of the cat5 and the pins sticking out the bottom of the jack. I get no signal connection. I assumed I may have messed up my soldering so I tried plugging the cat5 cable into one of the other ports still attached to the board and I this time tested continuity from the cable to the still soldered pins showing on the back side of the board.
Is there some kind of gate or diode mechanism in the cat5 receiving jack that keeps it from having signal pass through until enabled?
Best Answer
Most devices in the last decade do not have plain RJ45 jacks. Due to micronization of components and the demand for smarter/smaller parts, RJ45 jacks have combined the Jack with the Magnetic Couplers that used to be separate parts.
Typical schematic for a Mag Jack:
That is a 2 pair, 100Base-T version. Some have the other 2 pairs connected to pins instead of shield. And Gigabit or 4 pair versions simply have 2 more sets of magnetic couplers.
Notice the IC next to this jack. That is an external magnetic coupler/transformer. If the router or device you pull your jack from does not have something similar, it most likely has a MagJack.:
