def signal(x, yT, T):
    Y=[]
    fp=open('testt.txt', 'w')
    fp.write('Xi\tYi\n')
    for ins in x:
        outs=(ins+T*yT)/(T+1)
        Y.append(outs)
        yT=outs
        fp.write(str(ins)+'\t'+str(outs)+'\n')
    fp.close
    return Y