mixing logical with real in equation

Hello,

I am looking at some fortran 90 source code that was apparently written
using Visual Fortran and am seeing something I have never seen before
and am surprised that it's legal (or is it?). The code apparently works
but when I compile using Forte on a Sun box it complains as I would
expect.

Here is a snippet of the code. Can someone explain to me how this can
be done and if it's legal?

NT=VSP(4,I)+.5
COND=-((K-1)*T2*(NT.EQ.1)+VOLT*(NT.EQ.2))

Thanks in advance.