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Thread: 16FT USB Cable Extension, Passive Vs Active?

  1. #1
    Variable Bitrate
    Join Date
    Oct 2004
    South Carolina

    16FT USB Cable Extension, Passive Vs Active?

    I'm browsing around to buy a long usb cable to run from the trunk to the dash.

    I've never heard of an "active" usb cable before, here's a quote from the site:
    16FT 5M USB 2.0/1.0 Active Extension / Repeater Cable A Male to A Female [BL]

    The USB 2.0 Extension Cable is not a passive cable. It is an active device. The USB signals Going in and out of the extension cable are buffered to assure signal quality and the meeting of the USB's electrical and timing spec. Using passive cables for the purpose of extension Will result in signal errors and is not recommended.

    USB extension cable allows an USB device to have its cable length extended 16ft. The USB extension cable acts as a USB hub and buffers all sownstream and upstream data traffic. High spped, full-speed and low-speed devices will function equally well with the USB extension cable
    Would there be actually any gain in getting the more expensive "Active" cable vs the just a normal usb cable (passive)?

  2. #2
    Variable Bitrate Splash-X's Avatar
    Join Date
    Mar 2006
    Palm Harbor, FL
    Passive USB - the devices automatically lock to each other without needing any additional equipment

    Active - Acts as a USB hub and buffers all downstream and upstream data traffic. Both the low-speed, full-speed and high-speed USB devices will function equally well with the USB Extension Cable.

    Main difference? You'll find that passive cables can only send signals up to around 16ft (around 5 meters). You can mix and match the cables without any problems. Where active come in handy is when you want to run more than 16ft.

    You can do this:

    16ft Passive => 16ft Active => 16ft Passive

    Why? Beats me, if I were going that far I would just use all Active to ensure the best data transmission.

    Using it in the car and going less than 16ft total just use a 10ft Passive OR a 16ft Passive.

    From their excerpt it seems like they are talking about having a 6ft (passive) USB cable already hooked up to your printer and then using this extension to it. Similar to the diagram but in reverse, you would want the active at the device to "buffer" the first part and then the passive at the PC for transmission.

    What exactly is your plan of attack? In my car I used a passive cable from the PC out to a HUB under my seat. The hub acts as a Active device so no need for an active cable. From there I used the HUB to plugin a DVD Rom, GPS mouse, and the touchscreen.

    Based on the diagram I showed you we have PC => Passive => HUB (Active) => Passive (to device)

  3. #3
    Constant Bitrate RawsonDR's Avatar
    Join Date
    Dec 2005
    Dayton, OH
    I would only go that route if you were having real problems after using a standard cable. A lot of people here are successfully running USB from trunk to dash without special cables.

    If you can't keep the cable length under 15 feet, you might think about running a shorter cable to a discrete location between trunk and dash, and then mounting a USB hub there (assuming you are using a USB hub anyway) and then running standard cables the rest of the way from the hub to the dash. (like Splash said) Then again that may not be any cheaper depending on how many devices you have.

  4. #4
    Variable Bitrate Splash-X's Avatar
    Join Date
    Mar 2006
    Palm Harbor, FL
    I agree that they are a waste of money. Your money would be better spent on a USB 2.0 hub on the end so you can add other devices if you wern't planning on it.

    Here is some "light" reading about why you would need an active cable. This article is really only concerned with the "timing" aspect of USB:

    It should give you a bit of any idea of why one may need an Active cable. In our cases we all should not need one.

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