$on and $broadcast in angular

If you want to $broadcast use the $rootScope:

$scope.startScanner = function() {

    $rootScope.$broadcast('scanner-started');
}

And then to receive, use the $scope of your controller:

$scope.$on('scanner-started', function(event, args) {

    // do what you want to do
});

If you want you can pass arguments when you $broadcast:

$rootScope.$broadcast('scanner-started', { any: {} });

And then receive them:

$scope.$on('scanner-started', function(event, args) {

    var anyThing = args.any;
    // do what you want to do
});

Documentation for this inside the Scope docs.