# Part 15 FCC Rules - what's the deal with undesired operation? **URL:** \ **Category:** Factual Questions\ **Created:** [December 16, 2008, 8:14am UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373 "2008-12-16T08:14:08Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![ntcrawler](https://avatars.discourse-cdn.com/v4/letter/n/34f0e0/32.png) [@ntcrawler](https://boards.straightdope.com/u/ntcrawler)\ **Post date:** [December 16, 2008, 8:14am UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/1 "2008-12-16T08:14:08Z")
This has been bothering me for years and years. I draw your attention to the well known and commonly quoted Part 15 of the FCC Rules as printed on many electronic devices: _This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation._ (1) is simple enough but it’s (2) that bothers me. What do you mean this device MUSt accept any interference received? What if I don’t want it to accept any interference? What if I build it so that it doesn’t accept ANY interference? Why would I purposely want to have a device which could operate in an undesired fashion from interference? Am I not allowed to protect my devices from interference? What kind of pentalties will I be subjected to by the mighty FCC if I break (2)? ---
**Author:** ![IAmNotSpartacus](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@IAmNotSpartacus](https://boards.straightdope.com/u/IAmNotSpartacus)\ **Post date:** [December 16, 2008, 8:37am UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/2 "2008-12-16T08:37:32Z")
You would have no problems trying to engineer interference out of your device, indeed if you were a manufacturer you’d have an obligation to do so. See CFR Title 47 Part 15.13 (2) deals with the totem pole of interference, and who is responsible to manage interference when it does exist. Users of Part 15 devices have no recourse with the Commission when they receive interference, whereas Part 97 (amateur radio) devices do have recourse, and indeed the Commission can and will levy citations and forfeitures against those who cause interference, when appropriate. ---
**Author:** ![corkboard](https://avatars.discourse-cdn.com/v4/letter/c/e9bcb4/32.png) [@corkboard](https://boards.straightdope.com/u/corkboard)\ **Post date:** [December 16, 2008, 1:49pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/3 "2008-12-16T13:49:16Z")
When it says it _must accept any interference received_, it’s not saying the manufacturer must design it in such a way to receive interference, it’s saying if it does receive interference, the other device that is causing the interference is not obligated to mitigate or remediate that interference. Alternatively, if the device was operating under a different part of the licensed spectrum and not suffering interference, but a subsequent device was introduced to the same general area and caused interference with the first device, the subsequent device would be obligated to remediate the interference. The first device would not have to just “accept” it. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 16, 2008, 2:31pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/4 "2008-12-16T14:31:38Z")
Basically, what the law is saying is this: If you have a device that is sensitive to RF interference, you’d better designed it so that it is well-shielded, because all of the other devices out there meet the law with respect to how much RF they emit. You can’t come crying to us if some other FCC licensed device makes yours go bonkers; designed it so that it will work correctly with other devices that emit the maximum RF energy permitted by law. Been there, done that. ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [December 16, 2008, 3:28pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/5 "2008-12-16T15:28:28Z")
It sounds like _accepting interference_ is not a physical property of the device itself, then - right? It instead refers to the owner/operator of the device not having any legal recourse to such interference - they can’t legally force the interference-causer to stop. If I’m wrong about this, could somebody describe the opposite of “accepting interference”? ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [December 16, 2008, 3:37pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/6 "2008-12-16T15:37:11Z")
It’s the RF version of “don’t bother any of the paying guests and don’t complain if they pelt you with rocks”. ---
**Author:** ![Driver8](https://avatars.discourse-cdn.com/v4/letter/d/b5a626/32.png) [@Driver8](https://boards.straightdope.com/u/Driver8)\ **Post date:** [December 16, 2008, 3:53pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/7 "2008-12-16T15:53:39Z")
> [@ntcrawler](#): > > (1) is simple enough but it’s (2) that bothers me. What do you mean this device MUSt accept any interference received? What if I don’t want it to accept any interference? What if I build it so that it doesn’t accept ANY interference? Why would I purposely want to have a device which could operate in an undesired fashion from interference? Am I not allowed to protect my devices from interference? What kind of pentalties will I be subjected to by the mighty FCC if I break (2)? As other posters have mentioned, I think all they mean by “accept” is that it shouldn’t break when receiving interference from other devices. In other words, if other devices are causing interference that causes your device to break, you have no recourse and it is your fault. In other words, protect your device from unwanted interference, although it seems fine if the interference causes the device to work improperly temporarily. ---
**Author:** ![Driver8](https://avatars.discourse-cdn.com/v4/letter/d/b5a626/32.png) [@Driver8](https://boards.straightdope.com/u/Driver8)\ **Post date:** [December 16, 2008, 3:55pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/8 "2008-12-16T15:55:30Z")
> [@brad\_d](#): > > If I’m wrong about this, could somebody describe the opposite of “accepting interference”? A blue tooth device that violently explodes when inadvertently catching some ABBA greatest hits from a local radio station 🙂 ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 16, 2008, 4:18pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/9 "2008-12-16T16:18:36Z")
> [@Driver8](#): > > As other posters have mentioned, I think all they mean by “accept” is that it shouldn’t break when receiving interference from other devices. In other words, if other devices are causing interference that causes your device to break, you have no recourse and it is your fault. > > In other words, protect your device from unwanted interference, although it seems fine if the interference causes the device to work improperly temporarily. And remember, it in this case “your” means “the manufacturer.” If you (the owner) bought a device that freaks out when exposed to legal RF emissions, you are perfectly within your rights to complain to than manufacturer, on the grounds that the device is non-functional under normal operating conditions. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [December 16, 2008, 6:38pm UTC](https://boards.straightdope.com/t/part-15-fcc-rules-whats-the-deal-with-undesired-operation/477373/10 "2008-12-16T18:38:32Z")
> [@ntcrawler](#): > > This has been bothering me for years and years. I draw your attention to the well known and commonly quoted Part 15 of the FCC Rules as printed on many electronic devices: > > _This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation._ > > (1) is simple enough but it’s (2) that bothers me. What do you mean this device MUSt accept any interference received? What if I don’t want it to accept any interference? What if I build it so that it doesn’t accept ANY interference? Why would I purposely want to have a device which could operate in an undesired fashion from interference? Am I not allowed to protect my devices from interference? What kind of pentalties will I be subjected to by the mighty FCC if I break (2)? You are misinterpreting the sentence because you are misdefining “interference”. Other devices to not broadcast “interference”, they broadcast whatever they broadcast and those waves only become interference when they interfere with the operation of your device. If your device is not affected by them then they are not “interference” because they do not interfere. > [@](#): > > meriam- webster > > from Anglo-French (s’)entreferir to strike one another, from entre- inter- + ferir to strike, > > 1 : to interpose in a way that hinders or impedes : come into collision or be in opposition > 4 : to act reciprocally so as to augment, diminish, or otherwise affect one another —used of waves In other words, “interference” is the effect one signal has on another signal. “interference” of one single wave is like the sound of one hand clapping. The point is that you have no right to demand form other that they stop using their devices if and because they might interfere with yours. But if they don’t interfere there is no interference.