Below is a correction to a message I sent earlier today:


If you have plus and minus 5v you can do the following:

Put the TTL level signal through a 10K resistor to drive the base of a
2N3906, collector connected to -5v through a 1K resistor..  Emitter is
connected to 5v.  TTL high will result in an output at the collector of
the 3906 that will be -5v.  TTL low will result in +5v at the collector
of the 3906.
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
WFT Electronics    wft@frii.com   http://www.frii.com/~wft
Gus Calabrese      303 321-1119......voicemail
Lola Montes        1799 Uinta Street   Denver, CO 80220
EMERGENCY:   791 High Street     Estes Park, CO  80517
if no success with wft@frii.com, try .... wft@bigfoot.com