all checkboxes selected on selecting specific checkbox among multiple checkboxes which has [(ngModal)] in angular4

if i select one checkbox after it loops other checkboxes also gets selected automaticlly... how can i select only one?

Here is my code sample !

<form>
 <div class="choice">
  <div *ngFor="let opts of technologies; let i = index">
   <input name=""  value="" [(ngModel)]="technologies_value" 
    type="checkbox"/><span></span>
  </div>
 </div>
</form>