>I  want to design a small fire alarm panel for my home, to augment my
>existing alarms, using some sort of addressing scheme for the smoke
>detectors.  I plan to use two wire detectors that short the line when in
>alarm.  I had debated using a voltage divider system with a current=
 limiting
>line resistor as the top half, and different values of resistance between
>each detector and the line as the bottom half.  I would then use the=
 16c72's
>A/D capability to read the divider and determine which head(s) were in
>alarm.  Does anyone have an idea how to do this differently - possibly=
 using
>some sort of addressing scheme?  I know addressable detectors are=
 available,
>but I assume the algorithm used to read these is proprietory.

        Easy. Think about binary system

Bit     8       7       6       5       4       3       2       1
Value   128     64      32      16      8       4       2       1

        Now imagine it with resistors

        1280K   640K    320K    160K    80K     40K     20K     10K

        Each resistor connected (or shorted) in the line, would alter the value of=
 the resistance of the circuit. So you could measure it with your PIC.

        I though it at 06:30A coming from an all-niter. So if has any errors,=
 sorry me.


--------------8<-------Corte aqui-------8<--------------

        All the best!!!
        Alexandre Souza
        xandinho@interlink.com.br

--------------8<-------Corte aqui-------8<--------------

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