Robert,

I believe that the RS232 standard specifies + and - 12v for the signals.
It's just that to be a true signal, it hacannot fall below the + and - 3
volt
level.  Or is this what you were saying?


Regards,


Jim


-----Original Message-----
From: Robert Mellgren <robert.mellgren@VALHALLA.ORNSKOLDSVIK.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Saturday, May 15, 1999 1:56 PM
Subject: Signal loss!?


>hi there i seem to recall that RS232 transmissions should be done over
short
>cables. since there are only -3/+3v levels, is this true.
>
>Since this transfer shall travel from 0.3 M - 200M i may need a potent
>voltage level and a good shielding.
>
>Which do you think is the best way too boost such a signal, should i boost
>it straight from the output pin from the pic, with the help of a NPN
>transistor, that drains say.. 12v-24v then convert that level of voltage
>back to TTL with a 7805, is the 7805 fast enough? we are after all talking
>1200 baud here, i do not seem to find a datasheet that describes this.
>
>Or make some sort of optic transmission, ( which is less cheap ), via optic
>cables, the positive side of this is that it wont be affected by
>distrubances.
>
>Hit me with some of your experiences in this matter, It would be be most
>appreciated.
>
>
>Greets
>Robert
>
>input...input... i need.. input...