  Using different types of proximity potentials, we have examined the trend of
variations of barrier characteristics (barrier height and its position) as well
as fusion cross sections for 50 isotopic systems including various collisions
of C, O, Mg, Si, S, Ca, Ar, Ti and Ni nuclei with $1\leq N/Z < 1.6$ condition
for compound systems. The results of our studies reveal that the relationships
between increase of barrier positions and decrease of barrier heights are both
linear with increase of $N/Z$ ratio. Moreover, fusion cross sections also
enhance linearly with increase of this ratio.
