function toggle_outlet(svg) {
	let sub_dev = svg.parentElement;
	let params = {
		device_id: sub_dev.parentElement.parentElement.id,
		sub_dev_id: sub_dev.id
	};
	let query = Object.keys(params)
		.map(k => encodeURIComponent(k) + '=' + encodeURIComponent(params[k]))
		.join('&');
	fetch(window.location.href + 'toggle?' + query)
	.then(function(response) {
		if (!response.ok) { throw new Error('HTTP error, status = ' + response.status); }
		return response.json();
	})
	.then(function(json) {
		if (json[sub_dev.id]) {
			svg.classList.remove('off');
			svg.classList.add('on');
		} else {
			svg.classList.remove('on');
			svg.classList.add('off');
		}
	});
}