radio and ng-model

HTML

<body ng-app="app">
    <div ng-controller='controller'>
                oConfigTerminal value= <input type="text" ng-model="oConfigTerminal"/><br><br>
        
        <div ng-show="!oConnection.aOptions"
        ng-repeat="oConnection in oFormOptions.aStationaryConnections">
            <label>
                <input type="radio" name="connection" ng-model="$parent.oConfigTerminal" value="{{oConnection.id}}"
                />{{oConnection.sId}}</label>
        </div>
          
        
    </div>
</body>

JavaScript

app = angular.module('app', []);

app.controller('controller', function ($scope) {
    $scope.oFormOptions = {};
   $scope.oConfigTerminal.sId="dsl";
    $scope.oFormOptions.aStationaryConnections = [{
        id: 1,
        sId: "analog"
    }, {
        id: 2,
        sId: "isdn"

    }, {
        id: 3,
        sId: "dsl"
    }];
    
    // Trying to set the default value
   $scope.oConfigTerminal.sId="dsl";

});