[Arm-netbook] car "infotainment" doesn't upgrade....

[luke.leighton]

On Thu, Oct 24, 2013 at 3:50 PM, Derek <dlahouss at mtu.edu> wrote:
> luke.leighton <luke.leighton <at> gmail.com> writes:
>
>> it's because they use a
>> $0.15 part  <at>  433mhz with a wide-band reception instead of a $1 part
>> with proper narrow-band filtering.  i assume that this is also the
>> reason why, if you are locked out of your car, you can ask someone
>> with a GSM mobile phone to press a duplicate door-opener AT THEIR END
>> of the conversation...
>
> Luke, you said this with too straight a face.  Maybe you're just taking the
> piss,

 i'm not - it was however an apocryphal story.  good one, too :)

> but GSM uses a voice codec with between 3k and 12k of bandwidth.  If
> it's not an audible part of speech, the codec should drop it to the floor.

 my guess is that what's going on is that R.F.-level interference
between the transmitters is resulting in a transmission that the
broad-band car receiver ICs are capable of picking up, and that yes,
the modulation rate is within the bandwidth of GSM codecs.  if ever
you've stood next to a stereo with a GSM phone and got "b-bp, b-bp,
bzzzzz" when someone speaks, you'll have a ... ok you get the idea

 anyway back to it... :)

l.