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FOIL Filter Support


Here you will find frequently asked questions (FAQ) about FOIL EMI filters and troubleshooting suggestions. FOIL EMI filters do not require any special treatment. Insert the filter between two networking devices (or in the case of the FOIL USB 2.0 between a computer and USB device) and the filter will autonegotiate the connection between the two and should work seamlessly and invisibly. However, occasionally there is a communication problem or network/software hiccup that interferes with proper functioning. And less frequently, there is a hardware failure. In the event you have a problem or question about your FOIL filter, the answer may be here or you can always contact us directly for assistance.



FOIL Ethernet Filters


My filter doesn't work. What should I do?

In the event that your FOIL Ethernet filter fails to work or stops working, follow these instructions:

NOTE: FOIL Ethernet filters pass Ethernet packets ONLY. They will NOT pass other signals such as the tones or pulses used by network cable testers or digital phone signals that are not based on Ethernet (TCP/IP). The ONLY way to test a FOIL Ethernet filter is to connect the filter to a computing device and a network (or other computing device) and verify connectivity.

Step 1. Verify the filter is plugged in and the power supply is functioning. The power supply should be able to provide 5VDC and at least 2 amps to the filter. If necessary, use a multimeter to check that the power supply output is 5VDC or slightly higher.

Step 2. Check the input connector and make sure the pins are not bent and are properly aligned so they will come in contact with the cable connector pins.

Step 3. Do the same for the output connector and make sure the pins are not bent and are properly aligned so they will come in contact with the cable connector pins.

Step 4. Reset the computing device, network device and the filter at the same time, allow ample time for everything to come back up and check for network connectivity. The filter can be reset by unplugging the power supply for 5 seconds and then plugging it back in.

Step 5. If there is still no connectivity, try “repairing” the network connection on the computing device or force the computing device to release its IP address and renegotiate with the network for a new IP address.

Step 6. If you are connected to a managed switch (eg Cisco switch), it is possible that the switch is turning off the network connection because it sees the FOIL Ethernet Filter as an unauthorized network (the filter acts like its own switch to minimize traffic through the fiber connection). You will need to check with your IT department to see if they use Bridge Protocol Data Unit (BPDU) Guard or similar security feature. Alternatively, you can test the filter by disconnecting from the managed switch and using two computers or network devices through the filter instead.

Step 7. Finally, verify that your computing device, cables and network are functioning properly by directly connecting the computing device to the network. You MUST use the same computing device, cables and network connection to positively remove these variables as possible causes of the problem. For the cables, you should either use an RJ-45 coupler to connect the cables together, or test each cable separately.

Step 8. If there is still no connectivity, then the filter may be faulty. It will be necessary for you to contact us and arrange for an RMA number.

All FOIL Ethernet filters have a two year warranty from date of first sale.

Will the FOIL Ethernet Filter work on CAT5e / CAT6 / etc.?

It depends. CAT5/CAT6/CAT7/etc. are cabling standards (ie wire gauge, twists per foot, insulation material, etc.). What matters is what is being transmitted over the cables. If it is Ethernet, then the FOIL Ethernet filters will work. But CAT5/CAT6/CAT7/etc. are sometimes used to carry other things like proprietary data, power, thermostat signals, sound, etc. In those circumstances, the FOIL Ethernet filters will not work and will actually block the signals.

I need an RJ-45 filter. Will The FOIL Ethernet Filter work?

RJ-45 refers to the type of connector or jack (Registered Jack design #45). Just like the cabling question above, what matters is what is being transmitted through the connector/jack. If it is Ethernet, then the FOIL Ethernet filters will work. But RJ-45 connectors/jacks are sometimes used to carry other things like proprietary data, power, thermostat signals, sound, etc. In those circumstances, the FOIL Ethernet filters will not work and will block the signals.

I plugged my IP phone into a FOIL Ethernet filter, but the phone won't work. Is the filter broken?

Ethernet based telephone systems (IP Phones) typically use Power Over Ethernet (POE) to power the phone. FOIL Ethernet filters (with the exception of the GigaFOILv3-POE) do not pass power. To use your phone, you will need to use one of the following:
  • An AC adapter designed for use with your IP Phone. Usually IP phones have a DC jack just for this purpose. The downside is the adapter will be a significant source of RF emissions inside your enclosure/chamber.

  • A POE injector. These take the output from the filter and inject POE onto the cable which can then be plugged into the IP Phone. The downside is the injector will be a significant source of RF emissions inside your enclosure/chamber.

  • The GigaFOILv3-POE. This version of the FOIL Ethernet filter has a POE injector built into the filter. The filter is designed with additional shielding and absorption to reduce the RF emissions radiated into your enlcosure/chamber.

I'm using a FOIL Ethernet filter inside my enclosure/chamber and I'm seeing RF emissions radiating from the filter. Why is that?

FOIL Ethernet filters use fiber optics to bring the Ethernet signal into and out of the enclosure/chamber. This requires the use of circuit cards which results in some RF emissions inside the enclosure/chamber. We have added additional shielding and absorption to the output side of the filter (the side with the threaded penetration), so be sure the body of the filter is outside of the enclosure/chamber. However, there will always be some amount of RF emissions that leak into the enclosure/chamber (but it is significantly less than any other potential solution).

Is the output cable shielded? Why or why not?

The output cable is NOT shielded. During our initial testing, we determined that when no cable was plugged into the output jack, the unshielded cable radiated less than the shielded cable. If you want/need to use shielded cable to your device, you can attach a braided metal shielding sleeve around the threaded output and attach the other end of the shielding sleeve to an exposed circle of shielding on your cable.

Does it matter if the body of the filter is inside or outside the enclosure/chamber?

The output of the filter (the side with the threaded penetration) has significantly lower radiated RF emissions than the input (the body of the filter). If you don't care about RF emissions inside your enclosure/chamber, then no it does not matter if the body is inside or outside. The shielding effectiveness of the filter does not depend on the location of the body of the filter.



FOIL USB 2.0 Filters


My FOIL USB 2.0 filter stopped working. How do I reset it?

If you encounter a problem with your FOIL USB 2.0 filter, try resetting it by disconnecting all USB cables and the DC power cable for a few minutes. Reconnect the DC power cable first and then the USB cables. It is important to disconnect ALL cables and to reconnect in the order specified because the USB cables will power the filter circuit cards even when the DC power cable is disconnected and this may create an unstable situation and prevent the filter from truly resetting.

I'm seeing RF emissions coming from the FOIL USB 2.0 filter. What can I do to reduce them?

The FOIL USB 2.0 filter uses fiber optics to bring the USB signal into and out of the enclosure/chamber. This requires the use of circuit cards which results in some RF emissions inside the enclosure/chamber. We have added additional shielding and absorption to the outputs of the filter (the 4 USB cables coming from the threaded penetration), but there will always be some amount of RF emissions that leak into the enclosure/chamber. To reduce the emissions, ground the shielding of any unused output cables because they will act like antennas inside the enclosure/chamber (**Ground JUST the shielding and not the signal lines because this may cause irreparable damage to the filter).

The voltage/current at the USB outputs is not what I was expecting. Why is that?

The FOIL USB 2.0 follows the USB 2.0 standard which provides between 5.25 - 4.75 VDC and 500mA at the output. We target 5.1VDC, but the process of filtering the power (which is different from how we filter the data) creates a voltage drop that increases with current draw. Please note that the 500mA provided by USB 2.0 is often not sufficient to charge certain devices like phones or tablets. Those devices require the USB Battery Charging Specification which provides up to 1500mA.