radio체크시 input 활성화 시키기

//테이블 코딩
<TABLE width="100%" border="1" name="s_tel_info" id="s_tel_in" style="display: none">
   <TR>
    <TD width="15%"></TD>
    <TD><INPUT TYPE="radio" NAME="s_tel_youmu" value="n" onclick="s_tel_change(this.value);" checked>이동없음&nbsp;&nbsp;&nbsp;<INPUT
     TYPE="radio" NAME="s_tel_youmu" value="y" onclick="s_tel_change(this.value);">이동</TD>
   </TR>
   <TR>
    <TD></TD>
    <TD><INPUT TYPE="radio" NAME="s_tel_rel" value="본인" checked
     disabled="true">본인&nbsp;&nbsp;&nbsp;<INPUT TYPE="radio"
     NAME="s_tel_rel" value="가족" disabled="true">가족&nbsp;&nbsp;&nbsp;<INPUT
     TYPE="radio" NAME="s_tel_rel" value="기타" disabled="true">기타</TD>
   </TR>
   <TR>
    <TD></TD>
    <TD><INPUT TYPE="text" NAME="s_tel_name" disabled="true" width="70%"></TD>
   </TR>
   <TR>
    <TD></TD>
    <TD><INPUT TYPE="text" NAME="s_tel_jumin" disabled="true" width="70%"></TD>
   </TR>
</TABLE>

//스크립트 부분
function s_tel_change(val1){
 var chk = document.getElementById('s_tel_youmu');
 var val = chk.value;
 
 if (val1 =='y') {
  document.sign_form.s_tel_rel[0].disabled = false;
  document.sign_form.s_tel_rel[1].disabled = false;
  document.sign_form.s_tel_rel[2].disabled = false;
  document.sign_form.s_tel_name.disabled = false;
  document.sign_form.s_tel_jumin.disabled = false;
 }else if (val1 == 'n') {
  document.sign_form.s_tel_rel[0].disabled = true;
  document.sign_form.s_tel_rel[1].disabled = true;
  document.sign_form.s_tel_rel[2].disabled = true;
  document.sign_form.s_tel_name.disabled = true;
  document.sign_form.s_tel_jumin.disabled = true;  
 }
}