[mdlug] OT - IR jamming

[Robert Meier]

Gary et al,

>>  Alternate theory: have you ever noticed how the definition of
>>  a Class C consumer electronics device states, "this device
>>  *MUST* accept interference causing unwanted operation."
> Where is your source for this information?

I'm not sure when the "class C" stickers became popular.

My 1987 Realistic Chronosette fm/am/alarm clock has no
"warning sticker", though it does have an FCC ID.

My 1994 Hewlitt Packard A4033A monitor (with FCC ID) says
   "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."

My 2006 Dorcey hand-cranked flashlight (with no FCC ID) says
   "FCC Class C
    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."

I am quite confident that my flashlight radiates less electromagnetic
energy than it reflects on a sunny day.

The FCC rule involved:
  "15.5   General conditions of operation.
   (a) Persons operating intentional or unintentional radiators shall not be
   deemed to have any vested or recognizable right to continued use of any
   given  frequency  by  virtue of prior registration or certification of
   equipment,  or,  for power line carrier systems, on the basis of prior
   notification of use pursuant to  Sec. 90.63(g) of this chapter.

   (b) Operation of an intentional, unintentional, or incidental radiator is
   subject to the conditions that no harmful interference is caused and that
   interference must be accepted that may be caused by the operation of an
   authorized radio station, by another intentional or unintentional radiator,
   by industrial, scientific and medical (ISM) equipment, or by an incidental
   radiator.

   (c) The operator of a radio frequency device shall be required to cease
   operating the device upon notification by a Commission representative that
   the device is causing harmful interference. Operation shall not resume until
   the condition causing the harmful interference has been corrected."
	-- 47 CFR 15.5
           United States Code of Federal Regulations
	   Title 47 Part 15 Section 5
	   http://frwebgate.access.gpo.gov/cgi-bin/get-cfr.cgi?
	          TITLE=47&PART=15&SECTION=5&YEAR=2005&TYPE=PDF

The jurisdiction involved:
  "15.1   Scope of this part.
   (a)  This  part  sets  out the regulations under which an intentional,
   unintentional, or incidental radiator may be operated without an individual
   license. It also contains the technical specifications, administrative
   requirements and other conditions relating to the marketing of part 15
   devices.

   (b) The operation of an intentional or unintentional radiator that is not in
   accordance with the regulations in this part must be licensed pursuant to
   the provisions of section 301 of the Communications Act of 1934, as amended,
   unless otherwise exempted from the licensing requirements elsewhere in this
   chapter.

   (c)  Unless  specifically  exempted,  the operation or marketing of an
   intentional or unintentional radiator that is not in compliance with the
   administrative  and technical provisions in this part, including prior
   Commission authorization or verification, as appropriate, is prohibited
   under section 302 of the Communications Act of 1934, as amended, and subpart
   I of part 2 of this chapter. The equipment authorization and verification
   procedures are detailed in subpart J of part 2 of this chapter."
	-- 47 CFR 15.1

Why class C (intentional radiator)?
Why not class B (unintentional radiator)?

> Not really that is exactly what they say.
> I've often wondered that myself.
> Why not allow it to be shielded to prevent interference?
> In whose interest is requiring interference to be allowed?

By Fermat's principle, shielding works both ways.
Shielding against interference, is also shielding against radiation.

As written above, 15.5, you may shield, and are required to shield
or otherwise reduce unwanted emissions (15.209),
if necessary to prevent excessive radiation.



The danger of course is that as "interference must be accepted that
may be caused by the operation of an authorized radio station"
becomes "interference must be accepted ..." and then becomes
"[consumer electronic devices must be susceptible to any sort of
  jamming system which the government has at its disposal]"

The problem of course, is that like gun control laws,
legal restrictions on freedom-of-reception restrict the law-abiding
to a much greater degree than the criminal.

<SATIRE>
If you prohibit fire extinguishers
(only those careless with fire need them),
you may limit the law-abiding to cold cuts and salads,
but you'll do little or nothing to stop arsonists (or those who are careless).
</SATIRE>



"Congress shall make no law respecting an establishment of religion,
 or prohibiting the free exercise thereof; or abridging the freedom
 of speech, or of the press; or the right of the people peaceably to
 assemble, and to petition the government for a redress of grievances."
   -- United States Constitution, Ammendment I
	   becomes
"Congress shall not support any religion ..."
	   becomes
"[government must prohibit free exercise of religion in public]"





-- 
Bob

  Caution: all living mortals who read this must die.