Re: i-dropper

["Alan Vogel" <avogel2@xxxxxxxxxxxxx>]

RF can be made to be low range by limiting the transmit power, or by
reducing the coupling between transmitter and receiver.  The passive RFID
mentioned in my previous post is inherently short-range.

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:44324697.931315781@xxxxxxxxxxxxxxxx
> Actually, the range is very limited - 1m or so max. That makes it nearly
> imposasible to eavesdrop on it to steal the code. RF is inherently less
> secure.
>
> "Alan Vogel" <avogel2@xxxxxxxxxxxxx> wrote:
>
>>Ah, but then you would have to be almost on top of the sensor in order to
>>communicate.
>>
>>At that point it may be better to just touch the key to a mating pair of
>>contacts.  Or if ESD is an issue, use a wireless RFID like the one
>>mentioned
>>in the link below.
>>
>>But if you're indoors, I would think that the LED system should work most
>>of
>>the time.
>>
>>"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
>>news:44312be3.858943843@xxxxxxxxxxxxxxxx
>>> It should be easy to prevent sunlight from hitting the LED. You could
>>> make
>>> it the proverbial "light at the end of a tunnel". ;)
>>>
>>> Here's another link that shows it being used for a touchpad like input
>>> device.
>>>
>>>     http://mrl.nyu.edu/%7Ejhan/ledtouch/index.html
>>>
>>> "Alan Vogel" <avogel2@xxxxxxxxxxxxx> wrote:
>>>
>>>>A nice idea, but if this technique is used for keyless entry outdoors
>>>>then
>>>>I
>>>>would think that sunlight could saturate the LED.
>>>>
>>>>Here's another clever idea from MERL, based on an idea from Microchip's
>>>>old
>>>>"Designing For Dollars" competition.
>>>>
>>>>http://www.merl.com/papers/docs/TR2002-21.pdf
>>>>
>>>>
>>>>"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
>>>>news:442eaff2.696142765@xxxxxxxxxxxxxxxx
>>>>> Here's a really neat, super secure and super cheap way to implement
>>>>> things
>>>>> like keyless entry.
>>>>>
>>>>>     http://www.merl.com/reports/docs/TR2003-35.pdf
>>>>
>>>
>>
>