f[t_] = 1;
fc = 1;
fs[t_] = Sum[f[n/(2 fc)] (Sin[(Pi ( 2fc t -n))]/( Pi ( 2fc t -n))),{n,-50,50}];
Plot[f[1/(2fc)](Sin[(Pi ( 2fc t - 1))]/(Pi(2 fc t -1))),{t,-5,5},PlotRange->All]
Plot[fs[t],{t,-5,5},PlotRange->{All, {0,2}}]

Plot[fs[t],{t,-5,5},PlotRange->{All, {.99,1.01}}]