[vdr] Re: Toslink on J2

["Dr. Werner Fink" <werner@suse.de>]

On Sun, Feb 24, 2002 at 01:03:02AM +0100, Roland Praml wrote:
> > Homebrew or comercial one? I think it's the easiest way to solder one of
> > this Toshiba TOTX 178 found at reichelt.de for only EUR2.30  to J2 instead
> > of some "cheap" blackboxes...(same site, about 29 EUR) But I don't know if
> > it is that simple. Is it? As I read it expect's TTL Level, so it seems to
> be
> > that simple.. Can please sombody invite some guy's from Siemens to explain
> > their plans for J2? Thanks... 8-)
> 
> It works, I've tried a red LED and a 120 ohm resistor.
> http://members.tripod.com/~Psych/super-cheap-toslink.html
> it was really cheap :-)

To use coax with 75 Ohm impedance a small circuit like this may
help

          100nF   300 Ohm
signal  ----||----[==]---+------------- coax (<= 1V)
 <=5V                    |
                        [=] 75 Ohm
                         |
    Gnd -----------------+------------- coax shield


It's a simple voltage divider which fits on the coax side
the required 75 Ohm termination.  Nevertheless high frequence signals
will be sended through.  The capacity avoids lower frequencies
and direct current.  It is untested .. though ...

     Werner