function y= tel(t,a,b,c,d)
[n,m]=size(t);
y=zeros(t);
for j=1:m, for i=1:n
	if t(i,j) > a then
		if t(i,j) <=b then
		  y(i,j)= (t(i,j)-a)/ (b-a)
		elseif t(i,j) > b &  t(i,j) < c then
			y(i,j)= ones (t(i,j))
		elseif t(i,j)< d  then
			y(i,j)=(d-t(i,j))/(d-c)
	end
	end,
end,end,
endfunction
y1=tel(0:1:20,3,6,9,12)