AngularJS Isolated Integration Sample

isolated.js

/*
 @, &, = integration scope
 <div ng-app="phoneApp">
 <div ng-controller="AppCtrl">
 <phone number="1111111" network="network" make-call="leaveVoicemail(number, message)"></phone>
 <phone number="2222222" network="network" make-call="leaveVoicemail(number, message)"></phone>
 <phone number="3333333" network="network" make-call="leaveVoicemail(number, message)"></phone>

 </div>
 </div>
*/

var app = angular.module("phoneApp", []);

app.controller("AppCtrl", function($scope) {
    $scope.leaveVoicemail = function(number, message) {
        alert("Number: " + number + " said: " + message);
    }
})

app.directive("phone", function() {
    return {
        restrict: "E",
        scope: {
            number: "@",  // local scope property
            network: "=", // bi-directional binding between local property and parent property
            makeCall: "&" // send expressions to parent scope
        },
        template: '<div class="panel">Number: {{number}} Network:<select ng-model="network" ng-options="network for network in networks">' +
            '</select></div><input type="text" ng-model="value">' +
            '<div class="button" ng-click="makeCall({number: number, message:value})">Call Home</div> ',
        link: function(scope) {
            scope.networks = ["KT", "SKT", "LGU+"];
            scope.network = scope.networks[0];
        }
    }
})

One thing I don't understand why "makeCall "is use as "make-call "in element phone ?????????