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'[ot]:keyless entry question'
2002\01\16@110845 by Douglas Butler

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I thought I knew basically how the rolling code keyless entry systems
work: the transmitter and receiver generate matched pseudorandom
sequences, the receiver has to look several codes foreward of the
current code in case someone hit the button while out of range, etc.

My question is how do they handle multiple transmitters?  My wife's car
has two transmitters and one sits on the shelf for months on end, but
both work.  Does the receiver have to know there are multiple
transmitters out there and keep track of pseudorandom sequences for
each?

Sherpa Doug

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2002\01\16@121416 by Tsvetan Usunov

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>I thought I knew basically how the rolling code keyless entry systems
>work: the transmitter and receiver generate matched pseudorandom
>sequences, the receiver has to look several codes foreward of the
>current code in case someone hit the button while out of range, etc.
>
>My question is how do they handle multiple transmitters?  My wife's car
>has two transmitters and one sits on the shelf for months on end, but
>both work.  Does the receiver have to know there are multiple
>transmitters out there and keep track of pseudorandom sequences for
>each?

the simple answer is: yes, they keep track for each transmitter

Best regards
Tsvetan
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2002\01\16@142905 by Andrew Warren

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Douglas Butler <PICLISTspamKILLspammitvma.mit.edu> wrote:

> I thought I knew basically how the rolling code keyless entry systems
> work: the transmitter and receiver generate matched pseudorandom
> sequences, the receiver has to look several codes foreward of the
> current code in case someone hit the button while out of range, etc.
>
> My question is how do they handle multiple transmitters?  My wife's car
> has two transmitters and one sits on the shelf for months on end, but
> both work.  Does the receiver have to know there are multiple
> transmitters out there and keep track of pseudorandom sequences for
> each?

Doug:

No, the receivers don't HAVE to work that way, but most of them do.

-Andy

=== Andrew Warren -- .....aiwKILLspamspam.....cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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