>The level shifter is to be able to communicate with the PC serial port.
The
>Nokia data cable you are talking about has exactly that inside it (max232
or
>similar). However, if you are doing PIC <-> phone directly there is no
need
>to first level shift to PC serial port levels and then shift back down to
>Nokia phone levels. I.e. why the mediator? Do a search on the web for
>home-built Nokia data cables, and they're all very simple circuits with a
>direct mapping of phone pins to serial pins with the max232 in the middle.
>
>You should be able to connect your PIC directly to those pins, since you
have
>no need for the PC. Thus, no need for a max232 circuit or data cable.

most cell phones use 3V  power supply so level shifter will be necessary if
your PIC works on 5V (and you don't want to blow your phone output buffer)

Best regards
Tsvetan
---
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