C----------------------------------------------------------------------
        subroutine ftswby(buffer,npix)
C
C       swap pairs of bytes to convert I*2 values to/from IEEE
C
C       buffer  i  input buffer of 16-bit words to be swapped
C       npix    i  number of 16-bit words to be swapped
C
C       written by Wm Pence, HEASARC/GSFC, February 1991

        integer npix,k
        logical*1 buffer(npix*2),temp

        do 10 k=2,npix*2,2
           temp = buffer(k-1)
           buffer(k-1) = buffer(k)
           buffer(k) = temp
10      continue
        end