Why is filtering by checkbox not working in angular?

Question

Angular

Hello, tell me why the filter in angular does not work please.
The checkbox itself is

Моторола: <input type="checkbox" ng-model="Motorola" ng-true-value='Motorola' ng-false-value=''> <br />

Output of the phones themselves

<div class="col-lg-4 col-md-4 col-sm-6 col-xs-12 phone" ng-repeat="phone in phones | filter:filter | filter:Dell | filter:Motorola">
        <img ng-src="{{phone.imageUrl}}" alt="{{phone.name}}">
        <h1>{{phone.name}}</h1>
        <p>{{phone.snippet}}</p>
        <strong>{{phone.price}} $</strong>
      </div>

I posted a little more extended code here jsfiddle.net/nujb85c6/#