Hi All,

Here is my two cents worth. (if it is worth anything)


When to test.
Any digital device that uses clock speeds equal to or greater than 9 kHz
must be tested.  Only computers and computer peripherals are allowed
Class A levels
when they are not home use, all other devices must meet Class B

When to involve the FCC.
Case 1
If the digital device is not a personal computer or personal computer
peripheral the manufacturer must keep a verification report on file.

Case 2
If the digital device is home use and is a personal computer or personal
computer peripheral the manufacturer can use the FCC Deceleration of
Conformity (FCC DoC) or Certification routes to authorization.  FCC DoC
requires testing be done at an accredited lab and no submittal to FCC.
With Certification use a lab listed (listed is not the same as
accredited) with the FCC, submit the report and $$$ fee to the FCC for
approval after 8 weeks.

Electronic copies of the latest CFR 47 Part 15, Subpart B are available
at the FCC web site, www.ffc.gov/oet

Rick Linford
DNB ENGINEERING, INC.


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Hi Jon, 

I'll take the plunge and give you some of 
my answers below ... 

> From: Jon Bertrand <[email protected]>
>      
>      Hello Everyone,
>      
>      A lot of "budding midnight designers" ask these questions on the 
>      microcontroller newsgroups so I thought I'd ask them here - and
learn 
>      something :)
>      
>      (If I've missed some FAQ that covers this please let me know.)
>      
>      1)  Say I'm building some microcontroller based widget in my home 
>      business that runs model trains (or whatever).  It's not an
intential 
>      transmitter, its typically used in the home.  And I want to sell
them. 
>      Do I need some FCC approval.

Yes. 

CFR 47 Part 15 specifies not only minimum 
frequencies at which your little device 
operates (I believe anything above 7kHz) 
but also power (I believe anything above 
picowatts). I'm positive someone here will 
list the specifics. I unfortunately do not 
have the standard in front of me. 

>      Specifically do I need to:
>      
>      1.a)  Spend money having someone test emissions.

Yes. For reason why see answer to 1.b) below. 

>      1.b)  File some paperwork with the FCC.

Yes. Since your device will be used in a residence, 
you will need Class B which involves registration. 
Registration will cost you. 

>      2)  If I don't have the money for testing - but I really do know how

>      to keep my microcontroller quiet (i.e I know loop area, di/dt, and 
>      maybe even have done lots of other 'approved' products)  - and a 
>      little in-home testing shows it doesn't bother the rabbit ears or 
>      show-up on the AM or FM radio.  Would I be in violation of some law
if 
>      I just sold the darn thing.

By the book, yes.  See CFR 47 Part 15. 

CFR I'm sure you know stands for Code of Federal Regulations, 
i.e. Federal Law. You're also assuming that the only reason 
you'll get in trouble is for interference.  Not really true. 
Take it to a trade show, have it be the quietest thing around, 
have some representative from the FCC look for a label or 
proof of testing and there is none, you're in trouble. 

What's the probability of this happening? 
Who knows... 

>      2.a)  Would I be in violation if it really was quiet to CISPR (i.e. 
>      would have passed).  (i.e. is there now a CE mark like compliance
that 
>      lets me self declare and assert who's responsible).

Woaw! Wait a minute.  CE mark?  Thought is was just FCC.  
You're going to Europe, haven't tested the device, 
are assuming it's quiet and yet you're marking it?  
Don't do it. 

This is not FCC approval. The FCC only validates testing 
for the US. It really doesn't approve anything (if I remember 
a previous discussion about this from way back). 

>      3)  How does the FCC verify that I don't pollute the EM band - do
they 
>      random sample train widgets or wait for someone to complain.

Depending upon some factors - both. 
Remember, the complaint could be from a competitor... 
I was at a trade show a long time ago where someone 
was yanked out of their booth by Federal Marshals. 

Bottom line for whoever is asking you, 
get it done, get the thing passed, 
then don't worry about it. 

Oh yea, don't forget about UL either.  ;) 

Regards,  Doug 


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