Angularjs：点击一下按钮

Question

       <tbody md-body>
          <tr md-row md-select="dessert"  md-select-id="name" ng-model="participant.partName" md-auto-select ng-repeat="participant in participants track by participant.partName | filter: search">
            <td md-cell>{{participant.partName}}</td>

            <td md-cell><img src="./images/mute.png" ng-click="mutePart(participant.partName);" title="Mute" 
                                ng-class="{'selected-image' : participant.partName === muteSelected}" /></td>
            <td md-cell><img src="./images/unmute.png"  ng-click="unmutePart(participant.partName);" title="Unmute" 
                                ng-class="{'selected-image' : participant.partName === unmuteSelected}"/></td>                  

          </tr>
        </tbody>

JS：

$scope.mutePart = function(muteSelected) {         
  $scope.muteSelected = muteSelected;
  $scope.unmuteSelected = null;
  $rootScope.muteInd = true;
  $rootScope.muted = true;

}

$scope.unmutePart = function(unmuteSelected) {
  $scope.unmuteSelected = unmuteSelected;
  $scope.muteSelected = null;
  $rootScope.mutInd = false;
  $rootScope.muted = false;
}

CSS：      .selected-image {border：1px solid red; }

我有各种端点的静音，取消静音图像按钮。对于第一个端点，单击静音，它会被选中但如果单击第二个端点的静音，则不再选择先前选择的第一个端点静音。我想保持所有点击的静音或取消静音按钮突出显示..目前只有一个按钮被点击选中。