I am trying to simulate JCHT35 switch to control a single actuator. There are 3 wires with an RJ45 tip plugged into the blackbox j45 female port connected to an actuator inside. What I am trying to do is connect the cat5 cable to my computer and black box and send a signal down to the actuator.

I guess in simplest terms, how do I just turn on lines on the ethernet port on my computer without using the ethernet protocol? Do I need to write a custom driver or are there any existing drivers that I can use?

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    \$\begingroup\$ You can't: there is a small transformer in the Ethernet output so that only high-frequency signals are transmitted and it's not possible to output a DC signal. Also, there is no reason for the pinout to line up. \$\endgroup\$
    – pjc50
    May 17, 2015 at 22:09
  • \$\begingroup\$ Indeed - even if you had a hypothetical embedded MCU where the ethernet pins also had GPIO functionality, that transformer is going to get in the way (and probably make driving them as GPIOs a bad idea). Look instead for GPIO pins, a local bus "parallel port" or a Serial UART, I2C, TWI, or USB port which could be bridged to one by means of an external micro or special function chip. \$\endgroup\$ May 17, 2015 at 22:33

1 Answer 1


This is not electrically possible. The connector is the same, yes, but what it is connected to internally is completely incompatible. You're going to have to buy or build some sort of interface board. A small microcontroller may be the best solution for this, either providing a completely self-contained solution or control via USB, serial, ethernet, or some other interface.


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