//Checks Map Area checkboxes on or off
function checkAll() {
	for (var i=0; i < document.searchmain.elements.length; i++) {
		if (document.searchmain.elements[i].type=="checkbox" && document.searchmain.elements[i].name!="s_all") {
			if (document.searchmain.elements[i].checked==false && document.searchmain.s_all.checked==true) {
				document.searchmain.elements[i].checked=true;
			} else {
				if (document.searchmain.elements[i].checked==true && document.searchmain.s_all.checked==false) {
					document.searchmain.elements[i].checked=false;
				}
			}
		}
	}
}
//Checks "Select All" checkbox on or off
function switchAll() {
	var bClear = false;
	for (var i=0; i < document.searchmain.elements.length; i++) {
		if (document.searchmain.elements[i].type=="checkbox" && document.searchmain.elements[i].name!="s_all") {
			if (document.searchmain.elements[i].checked==false) {
				bClear = true;
			}
		}
	}
	if (bClear==true) {
		document.searchmain.s_all.checked=false;
	} else {
		document.searchmain.s_all.checked=true;
	}
}
function validateSelection() {
	var bSelected = false;
	for (var i=0; i < document.searchmain.elements.length; i++) {
		if (document.searchmain.elements[i].type=="checkbox") {
			if (document.searchmain.elements[i].checked==true) {
				bSelected = true;
			}
		}
	}
	if (bSelected==true) {
		return true;
	} else {
		alert ("Please select at least one channel to search from.")
		return false;
	}
}