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

Put the TTL level signal through a 10K resitor to drive the base of a
2N3906, emitter connected to -5v through a 1K resistor..  Collector is
connected to 5v.  TTL high will result in an output at the emitter of
the 3906 that will be -5v.  TTL low will result in +5v at the emiiter of
the 3906.
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