var enabled = 0;

function TOfunc() {

TO = window.setTimeout( "TOfunc()", 1000
);

var today = new Date();

document.clock.disp.value =
today.toLocaleString();

}

</script>

<form name="clock">
<input type="text" name="disp" value="" size=20
onFocus="this.blur()" >
<br>
<input type="radio" name="rad" value="OFF"
checked
onClick="
if( enabled==1 )
{
document.clock.disp.value='';
clearTimeout( TO );
enabled = 0;
}
"> 关
<input type="radio" name="rad" value="on"
onClick="
if( enabled == 0 ) {
var TO = setTimeout( 'TOfunc()', 1000 );
enabled = 1; }" > 开
</form>