{"id":75,"date":"2009-10-21T21:26:18","date_gmt":"2009-10-22T01:26:18","guid":{"rendered":"http:\/\/blogs.law.harvard.edu\/niftyc\/?p=75"},"modified":"2011-07-29T22:50:47","modified_gmt":"2011-07-30T02:50:47","slug":"declaration-of-conformity-three-questions-about-unlicensed-wireless-devices","status":"publish","type":"post","link":"https:\/\/archive.blogs.harvard.edu\/niftyc\/archives\/75","title":{"rendered":"Declaration of Conformity: Three Questions About Unlicensed Wireless Devices"},"content":{"rendered":"

I was recently having a conversation about unlicensed wireless devices<\/strong>. \u00a0That is: \u00a0radio transmitters that don’t require advance permission from the government to operate (a license). \u00a0Examples of unlicensed devices are baby monitors and cordless phones. \u00a0You can buy them at Best Buy and you don’t need to have your own radio station call letters or pass a test. \u00a0One reason that people find unlicensed devices interesting is that they often have a lot of them sitting around their house<\/strong> or office.<\/p>\n

Some questions came up in the conversation and they are hard for me to answer. \u00a0I’m putting them up here as a way to document my attempts.<\/p>\n

Here’s the first one: \u00a0What frequency band contains the most unlicensed devices? <\/strong> “Most” in this case meant most diverse<\/strong>. \u00a0In other words: Where in the ether would we find the greatest diversity of different kinds of things sharing frequencies with each other? \u00a0My guess was the 2.4GHz band, as that is the frequency band that really popularized the idea of mainstream low-powered unlicensed devices for untrained consumers in the 1970s using spread spectrum techniques. \u00a0That’s where some of the most common devices today really took off. \u00a0Another good bet would be 900MHz, however. \u00a0(Amateur radio enthusiasts and engineers used devices without specific frequency licenses much earlier than that. \u00a0All of this is chronicled in Kenneth Carter’s Unlicensed to Kill<\/a>.)<\/p>\n

You could pick other bands as historically important but they didn’t really take off in the same way. \u00a0(I’m thinking of the U-PCS and U-NII bands.) \u00a0There is some more history in Henry Goldberg’s short paper Grazing on the Commons<\/a>, which also draws attention to of Silicon Valley’s interest in unlicensed wireless operation and includes the delightful quote:<\/p>\n

Like sin itself<\/strong>, the deliberate un-licensing of spectrum began with an Apple<\/strong>.<\/p><\/blockquote>\n

The next question: \u00a0Is there a list of all of the different kinds of things that operate in the band<\/strong>? \u00a0“Unlicensed” means the device operator doesn’t need permission but the device still needs to get one of those nifty FCC stickers on it — called certification. \u00a0Here’s a retro one.<\/p>\n

\"\"<\/p>\n

In some contexts this is called a “declaration of conformity<\/strong>.” \u00a0What a nice phrase! \u00a0Those administrative law regulators really have a way with words. \u00a0I’ll use it as my post title.<\/p>\n

So you can search the certifications<\/strong> online. \u00a0I searched 2400 – 2483 MHz (not exact match) in the charmingly not-user-friendly EAS database<\/a> at our own Federal Communications Commission (use “authorization search<\/a>“). \u00a0 It turns out there are 3001 different things certified to operate in that band right now. \u00a0The database is so hard to use that there is no easy way to see what the devices are without several clicks for each device. \u00a0I tried two at random and got (1) an off-brand wireless camera<\/strong> and (2) an old-looking GE cordless phone<\/strong>.<\/p>\n

Okay that didn’t really help. \u00a0Let me expand the question and just brainstorm instead. \u00a0Here’s question number three: Is there a list of all of the different kinds of unlicensed devices? <\/strong>Maybe I can brainstorm one. \u00a0I’ll see if I can list all of the examples of unlicensed transmitters that are intentionally transmitting. \u00a0My guess is that we can find examples of most of these (except as noted in parentheses) in the 2.4 GHz range.<\/p>\n