# "This device may not cause harmful interference..." **URL:** \ **Category:** Factual Questions\ **Created:** [February 1, 2006, 8:05pm UTC](https://boards.straightdope.com/t/this-device-may-not-cause-harmful-interference/342559 "2006-02-01T20:05:23Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![StewieGriffin420](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@StewieGriffin420](https://boards.straightdope.com/u/StewieGriffin420)\ **Post date:** [February 1, 2006, 8:05pm UTC](https://boards.straightdope.com/t/this-device-may-not-cause-harmful-interference/342559/1 "2006-02-01T20:05:23Z")
“but must accept any interference recieved” What is the deal with this FCC warning? So my electronics cannot cause interference, but if something else causes interference to my stuff I am just SOL? how is that fair? ---
**Author:** ![Fridgemagnet](https://avatars.discourse-cdn.com/v4/letter/f/22d042/32.png) [@Fridgemagnet](https://boards.straightdope.com/u/Fridgemagnet)\ **Post date:** [February 1, 2006, 8:16pm UTC](https://boards.straightdope.com/t/this-device-may-not-cause-harmful-interference/342559/2 "2006-02-01T20:16:13Z")
It means it must function as intended up to a specified level of electromagnetic interference, and itself only emit EMI below another specified level. Usually both radiated and conducted interference figures for susceptibility and emissions must be adhered to. EMI standards vary from country to country (though they are unified in the EU), and are also specific to the type of electrical appliance in question. There are many, many standards… ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 1, 2006, 8:26pm UTC](https://boards.straightdope.com/t/this-device-may-not-cause-harmful-interference/342559/3 "2006-02-01T20:26:52Z")
The intent of this section of Part 15 is to discourage modification of the product in the event that unforseen interference is caused by licensed use of the RF spectrum. The designers of the equipment have taken reasonable precautions to ensure that normal operation in the intended environment will 1) not interfere with licensed users of the spectrum and 2) that the device will function as intended in the presense of normal EMI emissions. You are not allowed to modify the product in the event that some sort of EMI _does_ cause the device to function improperly, since any such modification might unintentionally create an interference problem with licensed spectrum use. ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [February 1, 2006, 8:41pm UTC](https://boards.straightdope.com/t/this-device-may-not-cause-harmful-interference/342559/4 "2006-02-01T20:41:00Z")
I also liked the Cold War Era implications. You will not attempt to sheild the product to stop us from frying it with an electro magnetic pulse. You also will not try to stop it from accepting our jaming signal, if we decide to employ it. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 1, 2006, 9:16pm UTC](https://boards.straightdope.com/t/this-device-may-not-cause-harmful-interference/342559/5 "2006-02-01T21:16:59Z")
I should add that the other thing it does is to absolve licensed spectrum users of responsibility for problems their legally-operated equipment may cause to Part 15 certified devices: “Hey, your radio/TV/Ham station is making my computer keyboard type random garbage!” “Sorry, dude, not my fault. Part 15, y’know.”