Itr 1 u/s 10 allowance

In Form 16 Deduction showed Rs 20,000 as a other allowances . I asked to employer they told it is ' Telephone allowance" as i read about Telephone allowance it is fully taxable. 1} What I do in which section I can show the deduction ? 2} u/s 10 exempted allowances is less than 10% of gross so it compulsory to show allowances in ITR?