diff --git a/CHANGELOG b/CHANGELOG
index c35498cde..d965a89cd 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -11,33 +11,41 @@ Version 2.0.0 (unreleased)
 Agenda:
 - Updated the tests and changed only small internal parts of method of the
   agenda model. No API changes.
+- Deprecated mptt.
 Assignments:
-- Massive refactoring and cleanup of assignments app.
-- Renamed app from assignment to assignments
+- Renamed app from assignment to assignments.
+- Massive refactoring and cleanup of the app.
 Motions:
-- Renamed app from motion to motions
+- Renamed app from motion to motions.
 Mediafiles:
-- Renamed app from mediafile to mediafiles
+- Renamed app from mediafile to mediafiles.
 Users:
 - Massive refactoring of the participant app. Now called 'users'.
-- Used new anonymous user object instead of an authentification backend.
+- Used new anonymous user object instead of an authentification backend. Used
+  special authentication class for REST requests.
 - Used authentication frontend via AngularJS.
 Other:
 - New OpenSlides logo.
 - Changed supported Python version to >= 3.3.
 - Used Django 1.7 as lowest requirement.
 - Added Django's application configuration. Refactored loading of signals,
-  template signals and slides.
-- Added API using Django REST Framework 3.x. Added several views and mixins for
-  generic views in OpenSlides apps.
+  template signals and projector elements/slides.
+- Setup migrations.
+- Added API using Django REST Framework 3.x. Added several views and mixins
+  for generic views in OpenSlides apps.
+- Refactored projector API using metaclasses now.
+- Renamed SignalConnectMetaClass classmethod get_all_objects to get_all
+  (private API).
 - Used AngularJS with additional libraries for single page frontend.
-- Removed use of 'django.views.i18n.javascript_catalog'.
+- Removed use of 'django.views.i18n.javascript_catalog'. Used angular-gettext
+  now.
 - Updated to Bootstrap 3.
 - Used SockJS for automatic update of AngularJS driven single page frontend.
 - Refactored start script and management commands.
 - Refactored tests.
 - Used Bower and gulp to manage third party JavaScript and Cascading Style
   Sheets libraries.
+- Used setup.cfg for development tools.
 - Fixed bug in LocalizedModelMultipleChoiceField.
 
 
diff --git a/openslides/core/apps.py b/openslides/core/apps.py
index a458ba4c7..ca50324a6 100644
--- a/openslides/core/apps.py
+++ b/openslides/core/apps.py
@@ -6,27 +6,23 @@ class CoreAppConfig(AppConfig):
     verbose_name = 'OpenSlides Core'
 
     def ready(self):
-        # Load main menu entry and widgets.
+        # Load main menu entry, projector elements and widgets.
         # Do this by just importing all from these files.
-        from . import main_menu, widgets  # noqa
+        from . import main_menu, projector, widgets  # noqa
 
         # Import all required stuff.
         from django.db.models import signals
         from openslides.config.signals import config_signal
-        from openslides.projector.api import register_slide_model
         from openslides.utils.autoupdate import inform_changed_data_receiver
         from openslides.utils.rest_api import router
         from .signals import setup_general_config
-        from .views import CustomSlideViewSet, TagViewSet
+        from .views import CustomSlideViewSet, ProjectorViewSet, TagViewSet
 
         # Connect signals.
         config_signal.connect(setup_general_config, dispatch_uid='setup_general_config')
 
-        # Register slides.
-        CustomSlide = self.get_model('CustomSlide')
-        register_slide_model(CustomSlide, 'core/customslide_slide.html')
-
         # Register viewsets.
+        router.register('core/projector', ProjectorViewSet)
         router.register('core/customslide', CustomSlideViewSet)
         router.register('core/tag', TagViewSet)
 
diff --git a/openslides/core/exceptions.py b/openslides/core/exceptions.py
index 08bd4f270..01660ab6f 100644
--- a/openslides/core/exceptions.py
+++ b/openslides/core/exceptions.py
@@ -1,5 +1,9 @@
 from openslides.utils.exceptions import OpenSlidesError
 
 
+class ProjectorException(OpenSlidesError):
+    pass
+
+
 class TagException(OpenSlidesError):
     pass
diff --git a/openslides/core/migrations/0001_initial.py b/openslides/core/migrations/0001_initial.py
new file mode 100644
index 000000000..c1a8f29be
--- /dev/null
+++ b/openslides/core/migrations/0001_initial.py
@@ -0,0 +1,75 @@
+import jsonfield.fields
+from django.db import migrations, models
+
+import openslides.utils.models
+import openslides.utils.rest_api
+
+
+def add_default_projector(apps, schema_editor):
+    """
+    Adds default projector, welcome slide and activates clock and welcome
+    slide.
+    """
+    # We get the model from the versioned app registry;
+    # if we directly import it, it will be the wrong version.
+    CustomSlide = apps.get_model('core', 'CustomSlide')
+    custom_slide = CustomSlide.objects.create(
+        title='Welcome to OpenSlides',
+        weight=-500)
+    Projector = apps.get_model('core', 'Projector')
+    projector_config = [
+        {'name': 'core/clock'},
+        {'name': 'core/customslide', 'id': custom_slide.id}]
+    Projector.objects.create(config=projector_config)
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='CustomSlide',
+            fields=[
+                ('id', models.AutoField(serialize=False, primary_key=True, auto_created=True, verbose_name='ID')),
+                ('title', models.CharField(verbose_name='Title', max_length=256)),
+                ('text', models.TextField(verbose_name='Text', blank=True)),
+                ('weight', models.IntegerField(verbose_name='Weight', default=0)),
+            ],
+            options={
+                'ordering': ('weight', 'title'),
+            },
+            bases=(openslides.utils.rest_api.RESTModelMixin, openslides.utils.models.AbsoluteUrlMixin, models.Model),
+        ),
+        migrations.CreateModel(
+            name='Projector',
+            fields=[
+                ('id', models.AutoField(serialize=False, primary_key=True, auto_created=True, verbose_name='ID')),
+                ('config', jsonfield.fields.JSONField()),
+            ],
+            options={
+                'permissions': (
+                    ('can_see_projector', 'Can see the projector'),
+                    ('can_manage_projector', 'Can manage the projector'),
+                    ('can_see_dashboard', 'Can see the dashboard'),
+                    ('can_use_chat', 'Can use the chat')),
+            },
+            bases=(openslides.utils.rest_api.RESTModelMixin, models.Model),
+        ),
+        migrations.CreateModel(
+            name='Tag',
+            fields=[
+                ('id', models.AutoField(serialize=False, primary_key=True, auto_created=True, verbose_name='ID')),
+                ('name', models.CharField(verbose_name='Tag', unique=True, max_length=255)),
+            ],
+            options={
+                'permissions': (('can_manage_tags', 'Can manage tags'),),
+                'ordering': ('name',),
+            },
+            bases=(openslides.utils.rest_api.RESTModelMixin, openslides.utils.models.AbsoluteUrlMixin, models.Model),
+        ),
+        migrations.RunPython(
+            add_default_projector,
+        ),
+    ]
diff --git a/openslides/core/migrations/__init__.py b/openslides/core/migrations/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/openslides/core/models.py b/openslides/core/models.py
index 0749f7c6e..991840a71 100644
--- a/openslides/core/models.py
+++ b/openslides/core/models.py
@@ -1,62 +1,105 @@
-from django.core.urlresolvers import reverse
 from django.db import models
+from django.utils.translation import ugettext as _
 from django.utils.translation import ugettext_lazy, ugettext_noop
-# TODO: activate the following line after using the apploader
-# from django.contrib.auth import get_user_model
+from jsonfield import JSONField
 
-from openslides.projector.models import SlideMixin
 from openslides.utils.models import AbsoluteUrlMixin
+from openslides.utils.projector import ProjectorElement
 from openslides.utils.rest_api import RESTModelMixin
 
-# Imports the default user so that other apps can import it from here.
-# TODO: activate this with the new apploader
-# User = get_user_model()
+from .exceptions import ProjectorException
 
 
-class CustomSlide(RESTModelMixin, SlideMixin, AbsoluteUrlMixin, models.Model):
+class Projector(RESTModelMixin, models.Model):
     """
-    Model for Slides, only for the projector.
-    """
-    slide_callback_name = 'customslide'
+    Model for all projectors. At the moment we support only one projector,
+    the default projector (pk=1).
 
-    title = models.CharField(max_length=256, verbose_name=ugettext_lazy('Title'))
-    text = models.TextField(null=True, blank=True, verbose_name=ugettext_lazy('Text'))
-    weight = models.IntegerField(default=0, verbose_name=ugettext_lazy('Weight'))
+    If the config field is empty or invalid the projector shows a default
+    slide. To activate a slide and extra projector elements, save valid
+    JSON to the config field.
+
+    Example: [{"name": "core/customslide", "id": 2},
+              {"name": "core/countdown", "countdown_time": 20, "status": "stop"},
+              {"name": "core/clock", "stable": true}]
+
+    This can be done using the REST API with POST requests on e. g. the URL
+    /rest/core/projector/1/activate_projector_elements/. The data have to be
+    a list of dictionaries. Every dictionary must have at least the
+    property "name". The property "stable" is to set whether this element
+    should disappear on prune or clear requests.
+    """
+    config = JSONField()
 
     class Meta:
         """
-        General permissions that can not be placed at a specific app.
+        Contains general permissions that can not be placed in a specific app.
         """
         permissions = (
-            ('can_manage_projector', ugettext_noop('Can manage the projector')),
             ('can_see_projector', ugettext_noop('Can see the projector')),
+            ('can_manage_projector', ugettext_noop('Can manage the projector')),
             ('can_see_dashboard', ugettext_noop('Can see the dashboard')),
-            ('can_use_chat', ugettext_noop('Can use the chat')),
-        )
+            ('can_use_chat', ugettext_noop('Can use the chat')))
+
+    @property
+    def projector_elements(self):
+        """
+        A generator to retrieve all projector elements given in the config
+        field. For every element the method get_data() is called and its
+        result returned.
+        """
+        elements = {}
+        for element in ProjectorElement.get_all():
+            elements[element.name] = element
+        for config_entry in self.config:
+            name = config_entry.get('name')
+            element = elements.get(name)
+            data = {'name': name}
+            if element is None:
+                data['error'] = _('Projector element does not exist.')
+            else:
+                try:
+                    data.update(element.get_data(
+                        projector_object=self,
+                        config_entry=config_entry))
+                except ProjectorException as e:
+                    data['error'] = str(e)
+            yield data
+
+
+class CustomSlide(RESTModelMixin, AbsoluteUrlMixin, models.Model):
+    """
+    Model for slides with custom content.
+    """
+    title = models.CharField(
+        verbose_name=ugettext_lazy('Title'),
+        max_length=256)
+    text = models.TextField(
+        verbose_name=ugettext_lazy('Text'),
+        blank=True)
+    weight = models.IntegerField(
+        verbose_name=ugettext_lazy('Weight'),
+        default=0)
+
+    class Meta:
+        ordering = ('weight', 'title', )
 
     def __str__(self):
         return self.title
 
-    def get_absolute_url(self, link='update'):
-        if link == 'update':
-            url = reverse('customslide_update', args=[str(self.pk)])
-        elif link == 'delete':
-            url = reverse('customslide_delete', args=[str(self.pk)])
-        else:
-            url = super().get_absolute_url(link)
-        return url
-
 
 class Tag(RESTModelMixin, AbsoluteUrlMixin, models.Model):
     """
-    Model to save tags.
+    Model for tags. This tags can be used for other models like agenda items,
+    motions or assignments.
     """
-
-    name = models.CharField(max_length=255, unique=True,
-                            verbose_name=ugettext_lazy('Tag'))
+    name = models.CharField(
+        verbose_name=ugettext_lazy('Tag'),
+        max_length=255,
+        unique=True)
 
     class Meta:
-        ordering = ['name']
+        ordering = ('name',)
         permissions = (
             ('can_manage_tags', ugettext_noop('Can manage tags')), )
 
diff --git a/openslides/core/projector.py b/openslides/core/projector.py
new file mode 100644
index 000000000..9c7c0315e
--- /dev/null
+++ b/openslides/core/projector.py
@@ -0,0 +1,81 @@
+from django.utils.timezone import now
+from django.utils.translation import ugettext as _
+
+from openslides.utils.projector import ProjectorElement
+
+from .exceptions import ProjectorException
+from .models import CustomSlide
+
+
+class CustomSlideSlide(ProjectorElement):
+    """
+    Slide definitions for custom slide model.
+    """
+    name = 'core/customslide'
+    scripts = 'core/customslide_slide.js'
+
+    def get_context(self):
+        pk = self.config_entry.get('id')
+        if not CustomSlide.objects.filter(pk=pk).exists():
+            raise ProjectorException(_('Custom slide does not exist.'))
+        return [{
+            'collection': 'core/customslide',
+            'id': pk}]
+
+
+class Clock(ProjectorElement):
+    """
+    Clock on the projector.
+    """
+    name = 'core/clock'
+    scripts = 'core/clock.js'
+
+    def get_context(self):
+        return {'server_time': now().timestamp()}
+
+
+class Countdown(ProjectorElement):
+    """
+    Countdown on the projector.
+
+    To start the countdown write into the config field:
+
+        {
+            "countdown_time": <timestamp>,
+            "status": "go"
+        }
+
+    The timestamp is a POSIX timestamp (seconds) calculated from server
+    time, server time offset and countdown duration (countdown_time = now -
+    serverTimeOffset + duration).
+
+    To stop the countdown set the countdown time to the actual value of the
+    countdown (countdown_time = countdown_time - now + serverTimeOffset)
+    and set status to "stop".
+
+    To reset the countdown (it is not a reset in a functional way) just
+    change the countdown_time. The status value remain 'stop'.
+
+    To hide a running countdown add {"hidden": true}.
+    """
+    name = 'core/countdown'
+    scripts = 'core/countdown.js'
+
+    def get_context(self):
+        if self.config_entry.get('countdown_time') is None:
+            raise ProjectorException(_('No countdown time given.'))
+        if self.config_entry.get('status') is None:
+            raise ProjectorException(_('No status given.'))
+        return {'server_time': now().timestamp()}
+
+
+class Message(ProjectorElement):
+    """
+    Short message on the projector. Rendered as overlay.
+    """
+    name = 'core/message'
+    scripts = 'core/message.js'
+
+    def get_context(self):
+        if self.config_entry.get('message') is None:
+            raise ProjectorException(_('No message given.'))
diff --git a/openslides/core/serializers.py b/openslides/core/serializers.py
index 30e0ae83d..bd3eef7fe 100644
--- a/openslides/core/serializers.py
+++ b/openslides/core/serializers.py
@@ -1,6 +1,39 @@
-from openslides.utils.rest_api import ModelSerializer
+from openslides.utils.rest_api import Field, ModelSerializer, ValidationError
 
-from .models import CustomSlide, Tag
+from .models import CustomSlide, Projector, Tag
+
+
+class JSONSerializerField(Field):
+    """
+    Serializer for projector's JSONField.
+    """
+    def to_internal_value(self, data):
+        """
+        Checks that data is a list of dictionaries. Every dictionary must have
+        a key 'name'.
+        """
+        if type(data) is not list:
+            raise ValidationError('Data must be a list of dictionaries.')
+        for element in data:
+            if type(element) is not dict:
+                raise ValidationError('Data must be a list of dictionaries.')
+            elif element.get('name') is None:
+                raise ValidationError("Every dictionary must have a key 'name'.")
+        return data
+
+    def to_representation(self, value):
+        return value
+
+
+class ProjectorSerializer(ModelSerializer):
+    """
+    Serializer for core.models.Projector objects.
+    """
+    config = JSONSerializerField()
+
+    class Meta:
+        model = Projector
+        fields = ('config', 'projector_elements', )
 
 
 class CustomSlideSerializer(ModelSerializer):
@@ -9,7 +42,7 @@ class CustomSlideSerializer(ModelSerializer):
     """
     class Meta:
         model = CustomSlide
-        fields = ('id', 'title', 'text', 'weight',)
+        fields = ('id', 'title', 'text', 'weight', )
 
 
 class TagSerializer(ModelSerializer):
@@ -18,4 +51,4 @@ class TagSerializer(ModelSerializer):
     """
     class Meta:
         model = Tag
-        fields = ('id', 'name',)
+        fields = ('id', 'name', )
diff --git a/openslides/core/views.py b/openslides/core/views.py
index e9175476a..935d1e132 100644
--- a/openslides/core/views.py
+++ b/openslides/core/views.py
@@ -21,14 +21,24 @@ from openslides.utils.plugins import (
     get_plugin_verbose_name,
     get_plugin_version,
 )
-from openslides.utils.rest_api import ModelViewSet
+from openslides.utils.rest_api import (
+    ModelViewSet,
+    ReadOnlyModelViewSet,
+    Response,
+    ValidationError,
+    detail_route
+)
 from openslides.utils.signals import template_manipulation
 from openslides.utils.widgets import Widget
 
 from .exceptions import TagException
 from .forms import SelectWidgetsForm
-from .models import CustomSlide, Tag
-from .serializers import CustomSlideSerializer, TagSerializer
+from .models import CustomSlide, Projector, Tag
+from .serializers import (
+    CustomSlideSerializer,
+    ProjectorSerializer,
+    TagSerializer,
+)
 
 
 class IndexView(utils_views.CSRFMixin, utils_views.View):
@@ -46,6 +56,192 @@ class IndexView(utils_views.CSRFMixin, utils_views.View):
         return HttpResponse(content)
 
 
+class ProjectorViewSet(ReadOnlyModelViewSet):
+    """
+    API endpoint to list, retrieve and update the projector slide info.
+    """
+    queryset = Projector.objects.all()
+    serializer_class = ProjectorSerializer
+
+    def check_permissions(self, request):
+        """
+        Calls self.permission_denied() if the requesting user has not the
+        permission to see the projector and in case of an update request the
+        permission to manage the projector.
+        """
+        manage_methods = (
+            'activate_elements',
+            'prune_elements',
+            'deactivate_elements',
+            'clear_elements')
+        if (not request.user.has_perm('core.can_see_projector') or
+                (self.action in manage_methods and
+                 not request.user.has_perm('core.can_manage_projector'))):
+            self.permission_denied(request)
+
+    @detail_route(methods=['post'])
+    def activate_elements(self, request, pk):
+        """
+        REST API operation to activate projector elements. It expects a POST
+        request to /rest/core/projector/<pk>/activate_elements/ with a list
+        of dictionaries to append to the projector config entry.
+        """
+        # Get config entry from projector model, add new elements and try to
+        # serialize. This raises ValidationErrors if the data is invalid.
+        projector_instance = self.get_object()
+        projector_config = projector_instance.config
+        for projector_element in request.data:
+            projector_config.append(projector_element)
+        serializer = self.get_serializer(projector_instance, data={'config': projector_config}, partial=False)
+        serializer.is_valid(raise_exception=True)
+        serializer.save()
+        return Response(serializer.data)
+
+    @detail_route(methods=['post'])
+    def prune_elements(self, request, pk):
+        """
+        REST API operation to activate projector elements. It expects a POST
+        request to /rest/core/projector/<pk>/prune_elements/ with a list of
+        dictionaries to write them to the projector config entry. All old
+        entries are deleted but not entries with stable == True.
+        """
+        # Get config entry from projector model, delete old and add new
+        # elements and try to serialize. This raises ValidationErrors if the
+        # data is invalid. Do not filter 'stable' elements.
+        projector_instance = self.get_object()
+        projector_config = [element for element in projector_instance.config if element.get('stable')]
+        projector_config.extend(request.data)
+        serializer = self.get_serializer(projector_instance, data={'config': projector_config}, partial=False)
+        serializer.is_valid(raise_exception=True)
+        serializer.save()
+        return Response(serializer.data)
+
+    @detail_route(methods=['post'])
+    def deactivate_elements(self, request, pk):
+        """
+        REST API operation to deactivate projector elements. It expects a
+        POST request to /rest/core/projector/<pk>/deactivate_elements/ with
+        a list of dictionaries. These are exactly the projector_elements in
+        the config that should be deleted.
+        """
+        # Check the data. It must be a list of dictionaries. Get config
+        # entry from projector model. Pop out the entries that should be
+        # deleted and try to serialize. This raises ValidationErrors if the
+        # data is invalid.
+        if not isinstance(request.data, list) or list(filter(lambda item: not isinstance(item, dict), request.data)):
+            raise ValidationError({'config': ['Data must be a list of dictionaries.']})
+
+        projector_instance = self.get_object()
+        projector_config = projector_instance.config
+        for entry_to_be_deleted in request.data:
+            try:
+                projector_config.remove(entry_to_be_deleted)
+            except ValueError:
+                # The entry that should be deleted is not on the projector.
+                pass
+        serializer = self.get_serializer(projector_instance, data={'config': projector_config}, partial=False)
+        serializer.is_valid(raise_exception=True)
+        serializer.save()
+        return Response(serializer.data)
+
+    @detail_route(methods=['post'])
+    def clear_elements(self, request, pk):
+        """
+        REST API operation to deactivate all projector elements but not
+        entries with stable == True. It expects a POST request to
+        /rest/core/projector/<pk>/clear_elements/.
+        """
+        # Get config entry from projector model. Then clear the config field
+        # and try to serialize. Do not remove 'stable' elements.
+        projector_instance = self.get_object()
+        projector_config = [element for element in projector_instance.config if element.get('stable')]
+        serializer = self.get_serializer(projector_instance, data={'config': projector_config}, partial=False)
+        serializer.is_valid(raise_exception=True)
+        serializer.save()
+        return Response(serializer.data)
+
+
+class CustomSlideViewSet(ModelViewSet):
+    """
+    API endpoint to list, retrieve, create, update and destroy custom slides.
+    """
+    queryset = CustomSlide.objects.all()
+    serializer_class = CustomSlideSerializer
+
+    def check_permissions(self, request):
+        """
+        Calls self.permission_denied() if the requesting user has not the
+        permission to manage projector.
+        """
+        if not request.user.has_perm('core.can_manage_projector'):
+            self.permission_denied(request)
+
+
+class TagViewSet(ModelViewSet):
+    """
+    API endpoint to list, retrieve, create, update and destroy tags.
+    """
+    queryset = Tag.objects.all()
+    serializer_class = TagSerializer
+
+    def check_permissions(self, request):
+        """
+        Calls self.permission_denied() if the requesting user has not the
+        permission to manage tags and it is a create, update or detroy request.
+        Users without permissions are able to list and retrieve tags.
+        """
+        if (self.action in ('create', 'update', 'destroy') and
+                not request.user.has_perm('core.can_manage_tags')):
+            self.permission_denied(request)
+
+
+class UrlPatternsView(utils_views.APIView):
+    """
+    Returns a dictionary with all url patterns as json. The patterns kwargs
+    are transformed using a colon.
+    """
+    URL_KWARGS_REGEX = re.compile(r'%\((\w*)\)s')
+    http_method_names = ['get']
+
+    def get_context_data(self, **context):
+        result = {}
+        url_dict = get_resolver(None).reverse_dict
+        for pattern_name in filter(lambda key: isinstance(key, str), url_dict.keys()):
+            normalized_regex_bits, p_pattern, pattern_default_args = url_dict[pattern_name]
+            url, url_kwargs = normalized_regex_bits[0]
+            result[pattern_name] = self.URL_KWARGS_REGEX.sub(r':\1', url)
+        return result
+
+
+class ErrorView(utils_views.View):
+    """
+    View for Http 403, 404 and 500 error pages.
+    """
+    status_code = None
+
+    def dispatch(self, request, *args, **kwargs):
+        http_error_strings = {
+            403: {'name': _('Forbidden'),
+                  'description': _('Sorry, you have no permission to see this page.'),
+                  'status_code': '403'},
+            404: {'name': _('Not Found'),
+                  'description': _('Sorry, the requested page could not be found.'),
+                  'status_code': '404'},
+            500: {'name': _('Internal Server Error'),
+                  'description': _('Sorry, there was an unknown error. Please contact the event manager.'),
+                  'status_code': '500'}}
+        context = {}
+        context['http_error'] = http_error_strings[self.status_code]
+        template_manipulation.send(sender=self.__class__, request=request, context=context)
+        response = render_to_response(
+            'core/error.html',
+            context_instance=RequestContext(request, context))
+        response.status_code = self.status_code
+        return response
+
+
+# TODO: Remove the following classes one by one.
+
 class DashboardView(utils_views.AjaxMixin, utils_views.TemplateView):
     """
     Overview over all possible slides, the overlays and a live view: the
@@ -175,33 +371,6 @@ class SearchView(_SearchView):
         return models
 
 
-class ErrorView(utils_views.View):
-    """
-    View for Http 403, 404 and 500 error pages.
-    """
-    status_code = None
-
-    def dispatch(self, request, *args, **kwargs):
-        http_error_strings = {
-            403: {'name': _('Forbidden'),
-                  'description': _('Sorry, you have no permission to see this page.'),
-                  'status_code': '403'},
-            404: {'name': _('Not Found'),
-                  'description': _('Sorry, the requested page could not be found.'),
-                  'status_code': '404'},
-            500: {'name': _('Internal Server Error'),
-                  'description': _('Sorry, there was an unknown error. Please contact the event manager.'),
-                  'status_code': '500'}}
-        context = {}
-        context['http_error'] = http_error_strings[self.status_code]
-        template_manipulation.send(sender=self.__class__, request=request, context=context)
-        response = render_to_response(
-            'core/error.html',
-            context_instance=RequestContext(request, context))
-        response.status_code = self.status_code
-        return response
-
-
 class CustomSlideViewMixin(object):
     """
     Mixin for for CustomSlide Views.
@@ -235,22 +404,6 @@ class CustomSlideDeleteView(CustomSlideViewMixin, utils_views.DeleteView):
     pass
 
 
-class CustomSlideViewSet(ModelViewSet):
-    """
-    API endpoint to list, retrieve, create, update and destroy custom slides.
-    """
-    queryset = CustomSlide.objects.all()
-    serializer_class = CustomSlideSerializer
-
-    def check_permissions(self, request):
-        """
-        Calls self.permission_denied() if the requesting user has not the
-        permission to manage projector.
-        """
-        if not request.user.has_perm('core.can_manage_projector'):
-            self.permission_denied(request)
-
-
 class TagListView(utils_views.AjaxMixin, utils_views.ListView):
     """
     View to list and manipulate tags.
@@ -327,37 +480,3 @@ class TagListView(utils_views.AjaxMixin, utils_views.ListView):
             action=getattr(self, 'action', None),
             error=getattr(self, 'error', None),
             **context)
-
-
-class TagViewSet(ModelViewSet):
-    """
-    API endpoint to list, retrieve, create, update and destroy tags.
-    """
-    queryset = Tag.objects.all()
-    serializer_class = TagSerializer
-
-    def check_permissions(self, request):
-        """
-        Calls self.permission_denied() if the requesting user has not the
-        permission to manage tags and it is a create, update or detroy request.
-        """
-        if (self.action in ('create', 'update', 'destroy') and
-                not request.user.has_perm('core.can_manage_tags')):
-            self.permission_denied(request)
-
-
-class UrlPatternsView(utils_views.APIView):
-    """
-    Returns a dictonary with all url patterns as json.
-    """
-    URL_KWARGS_REGEX = re.compile(r'%\((\w*)\)s')
-    http_method_names = ['get']
-
-    def get_context_data(self, **context):
-        result = {}
-        url_dict = get_resolver(None).reverse_dict
-        for pattern_name in filter(lambda key: isinstance(key, str), url_dict.keys()):
-            url = url_dict[pattern_name][0][0][0]
-            result[pattern_name] = self.URL_KWARGS_REGEX.sub(r':\1', url)
-
-        return result
diff --git a/openslides/users/apps.py b/openslides/users/apps.py
index 20d20d2bd..c04af0627 100644
--- a/openslides/users/apps.py
+++ b/openslides/users/apps.py
@@ -8,28 +8,23 @@ class UsersAppConfig(AppConfig):
     def ready(self):
         # Load main menu entry and widgets.
         # Do this by just importing all from these files.
-        from . import main_menu, widgets  # noqa
+        from . import main_menu, projector, widgets  # noqa
 
         # Import all required stuff.
         from openslides.config.signals import config_signal
         from openslides.core.signals import post_permission_creation
-        from openslides.projector.api import register_slide_model
         from openslides.utils.rest_api import router
         from .signals import create_builtin_groups_and_admin, setup_users_config
         from .views import GroupViewSet, UserViewSet
 
-        # Load User model.
-        User = self.get_model('User')
-
         # Connect signals.
-        config_signal.connect(setup_users_config, dispatch_uid='setup_users_config')
+        config_signal.connect(
+            setup_users_config,
+            dispatch_uid='setup_users_config')
         post_permission_creation.connect(
             create_builtin_groups_and_admin,
             dispatch_uid='create_builtin_groups_and_admin')
 
-        # Register slides.
-        register_slide_model(User, 'participant/user_slide.html')
-
         # Register viewsets.
         router.register('users/user', UserViewSet)
         router.register('users/group', GroupViewSet)
diff --git a/openslides/users/projector.py b/openslides/users/projector.py
new file mode 100644
index 000000000..a35ecacaf
--- /dev/null
+++ b/openslides/users/projector.py
@@ -0,0 +1,29 @@
+from django.utils.translation import ugettext as _
+
+from openslides.core.exceptions import ProjectorException
+from openslides.utils.projector import ProjectorElement
+
+from .models import User
+
+
+class UserSlide(ProjectorElement):
+    """
+    Slide definitions for user model.
+    """
+    name = 'users/user'
+    scripts = 'users/user_slide.js'
+
+    def get_context(self):
+        pk = self.config_entry.get('id')
+        try:
+            user = User.objects.get(pk=pk)
+        except User.DoesNotExist:
+            raise ProjectorException(_('User does not exist.'))
+        result = [{
+            'collection': 'users/user',
+            'id': pk}]
+        for group in user.groups.all():
+            result.append({
+                'collection': 'users/group',
+                'id': group.pk})
+        return result
diff --git a/openslides/utils/dispatch.py b/openslides/utils/dispatch.py
index df74630bf..09bb228ae 100644
--- a/openslides/utils/dispatch.py
+++ b/openslides/utils/dispatch.py
@@ -8,10 +8,9 @@ class SignalConnectMetaClass(type):
     value for each child class and None for base classes because they will
     not be connected to the signal.
 
-    The classmethod get_all_objects is added as get_all classmethod to every
-    class using this metaclass. Calling this on a base class or on child
-    classes will retrieve all connected children, one instance for each
-    child class.
+    The classmethod get_all is added to every class using this metaclass.
+    Calling this on a base class or on child classes will retrieve all
+    connected children, one instance for each child class.
 
     These instances will have a check_permission method which returns True
     by default. You can override this method to return False on runtime if
@@ -29,14 +28,17 @@ class SignalConnectMetaClass(type):
 
     class Base(object, metaclass=SignalConnectMetaClass):
         signal = django.dispatch.Signal()
+
+        def __init__(self, **kwargs):
+            pass
+
         @classmethod
         def get_dispatch_uid(cls):
             if not cls.__name__ == 'Base':
                 return cls.__name__
 
     class Child(Base):
-        def __init__(self, **kwargs):
-            pass
+        pass
 
     child = Base.get_all(request)[0]
     assert Child == type(child)
@@ -46,7 +48,7 @@ class SignalConnectMetaClass(type):
         Creates the class and connects it to the signal if so. Adds all
         default attributes and methods.
         """
-        class_attributes['get_all'] = get_all_objects
+        class_attributes['get_all'] = get_all
         new_class = super(SignalConnectMetaClass, metaclass).__new__(
             metaclass, class_name, class_parents, class_attributes)
         try:
@@ -70,18 +72,21 @@ class SignalConnectMetaClass(type):
 
 
 @classmethod
-def get_all_objects(cls, request):
+def get_all(cls, request=None):
     """
     Collects all objects of the class created by the SignalConnectMetaClass
     from all apps via signal. They are sorted using the get_default_weight
     method. Does not return objects where check_permission returns False.
 
-    Expects a django.http.HttpRequest object.
+    A django.http.HttpRequest object can optionally be given.
 
     This classmethod is added as get_all classmethod to every class using
     the SignalConnectMetaClass.
     """
-    all_objects = [obj for __, obj in cls.signal.send(sender=cls, request=request) if obj.check_permission()]
+    kwargs = {'sender': cls}
+    if request is not None:
+        kwargs['request'] = request
+    all_objects = [obj for __, obj in cls.signal.send(**kwargs) if obj.check_permission()]
     all_objects.sort(key=lambda obj: obj.get_default_weight())
     return all_objects
 
diff --git a/openslides/utils/projector.py b/openslides/utils/projector.py
new file mode 100644
index 000000000..629abe9b4
--- /dev/null
+++ b/openslides/utils/projector.py
@@ -0,0 +1,66 @@
+from django.dispatch import Signal
+
+from .dispatch import SignalConnectMetaClass
+
+
+class ProjectorElement(object, metaclass=SignalConnectMetaClass):
+    """
+    Base class for an element on the projector.
+
+    Every app which wants to add projector elements has to create classes
+    subclassing from this base class with different names. The name and
+    scripts attributes have to be set. The metaclass
+    (SignalConnectMetaClass) does the rest of the magic.
+    """
+    signal = Signal()
+    name = None
+    scripts = None
+
+    def __init__(self, **kwargs):
+        """
+        Initializes the projector element instance. This is done when the
+        signal is sent.
+
+        Because of Django's signal API, we have to take wildcard keyword
+        arguments. But they are not used here.
+        """
+        pass
+
+    @classmethod
+    def get_dispatch_uid(cls):
+        """
+        Returns the classname as a unique string for each class. Returns None
+        for the base class so it will not be connected to the signal.
+        """
+        if not cls.__name__ == 'ProjectorElement':
+            return cls.__name__
+
+    def get_data(self, projector_object, config_entry):
+        """
+        Returns all data to be sent to the client. The projector object and
+        the config entry have to be given.
+        """
+        self.projector_object = projector_object
+        self.config_entry = config_entry
+        assert self.config_entry.get('name') == self.name, (
+            'To get data of a projector element, the correct config entry has to be given.')
+        return {
+            'scripts': self.get_scripts(),
+            'context': self.get_context()}
+
+    def get_scripts(self):
+        """
+        Returns ...?
+        """
+        # TODO: Write docstring
+        if self.scripts is None:
+            raise NotImplementedError(
+                'A projector element class must define either a '
+                'get_scripts method or have a scripts argument.')
+        return self.scripts
+
+    def get_context(self):
+        """
+        Returns the context of the projector element.
+        """
+        return None
diff --git a/openslides/utils/rest_api.py b/openslides/utils/rest_api.py
index cb24813c0..19783bd50 100644
--- a/openslides/utils/rest_api.py
+++ b/openslides/utils/rest_api.py
@@ -6,6 +6,7 @@ from django.core.urlresolvers import reverse
 from rest_framework.decorators import detail_route  # noqa
 from rest_framework.serializers import (  # noqa
     CharField,
+    Field,
     IntegerField,
     ListSerializer,
     ModelSerializer,
@@ -15,7 +16,7 @@ from rest_framework.serializers import (  # noqa
     ValidationError)
 from rest_framework.response import Response  # noqa
 from rest_framework.routers import DefaultRouter
-from rest_framework.viewsets import ModelViewSet, ViewSet  # noqa
+from rest_framework.viewsets import ModelViewSet, ReadOnlyModelViewSet, ViewSet  # noqa
 from rest_framework.decorators import list_route  # noqa
 
 from .exceptions import OpenSlidesError
diff --git a/tests/integration/core/__init__.py b/tests/integration/core/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/integration/core/test_views.py b/tests/integration/core/test_views.py
new file mode 100644
index 000000000..671627d0f
--- /dev/null
+++ b/tests/integration/core/test_views.py
@@ -0,0 +1,46 @@
+import json
+
+from django.core.urlresolvers import reverse
+from rest_framework import status
+
+from openslides.utils.test import TestCase
+from openslides.core.models import CustomSlide, Projector
+
+
+class ProjectorAPI(TestCase):
+    """
+    Tests requests from the anonymous user.
+    """
+    def test_slide_on_default_projector(self):
+        self.client.login(username='admin', password='admin')
+        customslide = CustomSlide.objects.create(title='title_que1olaish5Wei7que6i', text='text_aishah8Eh7eQuie5ooji')
+        default_projector = Projector.objects.get(pk=1)
+        default_projector.config = [{'name': 'core/customslide', 'id': customslide.id}]
+        default_projector.save()
+
+        response = self.client.get(reverse('projector-detail', args=['1']))
+
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        self.assertEqual(json.loads(response.content.decode()), {
+            'config': [{'name': 'core/customslide', 'id': customslide.id}],
+            'projector_elements': [
+                {'name': 'core/customslide',
+                 'scripts': 'core/customslide_slide.js',
+                 'context': [
+                     {'collection': 'core/customslide',
+                      'id': customslide.id}]}]})
+
+    def test_invalid_slide_on_default_projector(self):
+        self.client.login(username='admin', password='admin')
+        default_projector = Projector.objects.get(pk=1)
+        default_projector.config = [{'name': 'invalid_slide'}]
+        default_projector.save()
+
+        response = self.client.get(reverse('projector-detail', args=['1']))
+
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        self.assertEqual(json.loads(response.content.decode()), {
+            'config': [{'name': 'invalid_slide'}],
+            'projector_elements': [
+                {'name': 'invalid_slide',
+                 'error': 'Projector element does not exist.'}]})
diff --git a/tests/old/core/models.py b/tests/old/core/models.py
deleted file mode 100644
index 421d4f5b2..000000000
--- a/tests/old/core/models.py
+++ /dev/null
@@ -1,12 +0,0 @@
-from django.db import models
-
-
-class TestModel(models.Model):
-    name = models.CharField(max_length='255')
-
-    def get_absolute_url(self, link='detail'):
-        if link == 'detail':
-            return 'detail-url-here'
-        if link == 'delete':
-            return 'delete-url-here'
-        raise ValueError('No URL for %s' % link)
diff --git a/tests/old/core/test_template_tags_filters.py b/tests/old/core/test_template_tags_filters.py
index e8eec4787..71e695316 100644
--- a/tests/old/core/test_template_tags_filters.py
+++ b/tests/old/core/test_template_tags_filters.py
@@ -3,8 +3,6 @@ from django.template import Context, Template
 from openslides.config.api import config
 from openslides.utils.test import TestCase
 
-from .models import TestModel
-
 
 class ConfigTagAndFilter(TestCase):
     def test_config_tag(self):
@@ -29,32 +27,3 @@ class ConfigTagAndFilter(TestCase):
         template = Template(template_code)
         self.assertTrue('FdgfkR04jtg9f8bq' in template.render(Context({})))
         self.assertFalse('bad_e0fvkfHFD' in template.render(Context({})))
-
-
-class AbsoluteUrlFilter(TestCase):
-    def setUp(self):
-        self.model = TestModel.objects.create(name='test_model')
-
-    def test_default_argument(self):
-        """
-        Test to call absolute_url without an argument.
-        """
-        t = Template("{% load tags %}URL: {{ model|absolute_url }}")
-        html = t.render(Context({'model': self.model}))
-        self.assertEqual(html, 'URL: detail-url-here')
-
-    def test_with_argument(self):
-        """
-        Test to call absolute_url with an argument.
-        """
-        t = Template("{% load tags %}URL: {{ model|absolute_url:'delete' }}")
-        html = t.render(Context({'model': self.model}))
-        self.assertEqual(html, 'URL: delete-url-here')
-
-    def test_wrong_argument(self):
-        """
-        Test to call absolute_url with a non existing argument.
-        """
-        t = Template("{% load tags %}URL: {{ model|absolute_url:'wrong' }}")
-        html = t.render(Context({'model': self.model}))
-        self.assertEqual(html, 'URL: ')
diff --git a/tests/old/core/test_views.py b/tests/old/core/test_views.py
index 54d709de9..a08953537 100644
--- a/tests/old/core/test_views.py
+++ b/tests/old/core/test_views.py
@@ -121,8 +121,8 @@ class CustomSlidesTest(TestCase):
 
     def test_update(self):
         # Setup
-        url = '/customslide/1/edit/'
-        CustomSlide.objects.create(title='test_title_jeeDeB3aedei8ahceeso')
+        custom_slide = CustomSlide.objects.create(title='test_title_jeeDeB3aedei8ahceeso')
+        url = '/customslide/%d/edit/' % custom_slide.pk
         # Test
         response = self.admin_client.get(url)
         self.assertTemplateUsed(response, 'core/customslide_update.html')
@@ -131,20 +131,9 @@ class CustomSlidesTest(TestCase):
             url,
             {'title': 'test_title_ai8Ooboh5bahr6Ee7goo', 'weight': '0'})
         self.assertRedirects(response, '/dashboard/')
-        self.assertEqual(CustomSlide.objects.get(pk=1).title,
+        self.assertEqual(CustomSlide.objects.get(pk=custom_slide.pk).title,
                          'test_title_ai8Ooboh5bahr6Ee7goo')
 
-    def test_delete(self):
-        # Setup
-        url = '/customslide/1/del/'
-        CustomSlide.objects.create(title='test_title_oyie0em1chieM7YohX4H')
-        # Test
-        response = self.admin_client.get(url)
-        self.assertRedirects(response, '/customslide/1/edit/')
-        response = self.admin_client.post(url, {'yes': 'true'})
-        self.assertRedirects(response, '/dashboard/')
-        self.assertFalse(CustomSlide.objects.exists())
-
 
 class TagListViewTest(TestCase):
     def test_get_tag_queryset(self):
diff --git a/tests/unit/core/test_views.py b/tests/unit/core/test_views.py
index 36f1df6b3..f146ad8dc 100644
--- a/tests/unit/core/test_views.py
+++ b/tests/unit/core/test_views.py
@@ -1,15 +1,16 @@
 from unittest import TestCase
-from unittest.mock import patch
+from unittest.mock import patch, MagicMock
 
 from openslides.core import views
+from openslides.utils.rest_api import ValidationError
 
 
 class TestUrlPatternsView(TestCase):
     @patch('openslides.core.views.get_resolver')
     def test_get_context_data(self, mock_resolver):
         mock_resolver().reverse_dict = {
-            'url_pattern1': [[['my_url1']]],
-            'url_pattern2': [[['my_url2/%(kwarg)s/']]],
+            'url_pattern1': ([['my_url1', [None]]], None, None),
+            'url_pattern2': ([['my_url2/%(kwarg)s/', ['kwargs']]], None, None),
             ('not_a_str', ): [[['not_a_str']]]}
         view = views.UrlPatternsView()
 
@@ -19,3 +20,127 @@ class TestUrlPatternsView(TestCase):
             context,
             {'url_pattern1': 'my_url1',
              'url_pattern2': 'my_url2/:kwarg/'})
+
+
+@patch('openslides.core.views.ProjectorViewSet.get_object')
+class ProjectorAPI(TestCase):
+    def setUp(self):
+        self.viewset = views.ProjectorViewSet()
+        self.viewset.format_kwarg = None
+
+    def test_activate_elements(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_Du4tie7foosahnoofahg',
+            'test_key_Eek8eipeingulah3aech': 'test_value_quuupaephuY7eoLohbee'}]
+        request = MagicMock()
+        request.data = [{'name': 'new_test_projector_element_el9UbeeT9quucesoyusu'}]
+        self.viewset.request = request
+        self.viewset.activate_elements(request=request, pk=MagicMock())
+        self.assertEqual(len(mock_object.return_value.config), 2)
+
+    def test_activate_elements_no_list(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_ahshaiTie8xie3eeThu9',
+            'test_key_ohwa7ooze2angoogieM9': 'test_value_raiL2ohsheij1seiqua5'}]
+        request = MagicMock()
+        request.data = {'name': 'new_test_projector_element_buuDohphahWeeR2eeQu0'}
+        self.viewset.request = request
+        with self.assertRaises(ValidationError):
+            self.viewset.activate_elements(request=request, pk=MagicMock())
+
+    def test_activate_elements_bad_element(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_ieroa7eu3aechaip3eeD',
+            'test_key_mie3Eeroh9rooKeinga6': 'test_value_gee1Uitae6aithaiphoo'}]
+        request = MagicMock()
+        request.data = [{'bad_quangah1ahoo6oKaeBai': 'value_doh8ahwe0Zooc1eefu0o'}]
+        self.viewset.request = request
+        with self.assertRaises(ValidationError):
+            self.viewset.activate_elements(request=request, pk=MagicMock())
+
+    def test_prune_elements(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_Oc7OhXeeg0poThoh8boo',
+            'test_key_ahNei1ke4uCio6uareef': 'test_value_xieSh4yeemaen9oot6ki'}]
+        request = MagicMock()
+        request.data = [{
+            'name': 'test_projector_element_bohb1phiebah5TeCei1N',
+            'test_key_gahSh9otu6aeghaiquie': 'test_value_aeNgee2Yeeph4Ohru2Oo'}]
+        self.viewset.request = request
+        self.viewset.prune_elements(request=request, pk=MagicMock())
+        self.assertEqual(len(mock_object.return_value.config), 1)
+
+    def test_prune_elements_with_stable(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_aegh2aichee9nooWohRu',
+            'test_key_wahlaelahwaeNg6fooH7': 'test_value_taePie9Ohxohja4ugisa',
+            'stable': True}]
+        request = MagicMock()
+        request.data = [{
+            'name': 'test_projector_element_yei1Aim6Aed1po8eegh2',
+            'test_key_mud1shoo8moh6eiXoong': 'test_value_shugieJier6agh1Ehie3'}]
+        self.viewset.request = request
+        self.viewset.prune_elements(request=request, pk=MagicMock())
+        self.assertEqual(len(mock_object.return_value.config), 2)
+
+    def test_deactivate_elements(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_c6oohooxugiphuuM6Wee',
+            'test_key_eehiloh7mibi7ur1UoB1': 'test_value_o8eig1AeSajieTh6aiwo'}]
+        request = MagicMock()
+        request.data = [{
+            'name': 'test_projector_element_c6oohooxugiphuuM6Wee',
+            'test_key_eehiloh7mibi7ur1UoB1': 'test_value_o8eig1AeSajieTh6aiwo'}]
+        self.viewset.request = request
+        self.viewset.deactivate_elements(request=request, pk=MagicMock())
+        self.assertEqual(len(mock_object.return_value.config), 0)
+
+    def test_deactivate_elements_wrong_element(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_c6oohooxugiphuuM6Wee',
+            'test_key_eehiloh7mibi7ur1UoB1': 'test_value_o8eig1AeSajieTh6aiwo'}]
+        request = MagicMock()
+        request.data = [{'name': 'wrong name'}]
+        self.viewset.request = request
+        self.viewset.deactivate_elements(request=request, pk=MagicMock())
+        self.assertEqual(len(mock_object.return_value.config), 1)
+
+    def test_deactivate_elements_no_list(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_Au1ce9nevaeX7zo4ye2w',
+            'test_key_we9biiZ7bah4Sha2haS5': 'test_value_eehoipheik6aiNgeegor'}]
+        request = MagicMock()
+        request.data = 'bad_value_no_list_ohchohWee1fie0SieTha'
+        self.viewset.request = request
+        with self.assertRaises(ValidationError):
+            self.viewset.deactivate_elements(request=request, pk=MagicMock())
+
+    def test_deactivate_elements_bad_list(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_teibaeRaim1heiCh6Ohv',
+            'test_key_uk7wai7eiZieQu0ief3': 'test_value_eeghisei3ieGh3ieb6ae'}]
+        request = MagicMock()
+        # Value 1 is not an dictionary so we expect ValidationError.
+        request.data = [1]
+        self.viewset.request = request
+        with self.assertRaises(ValidationError):
+            self.viewset.deactivate_elements(request=request, pk=MagicMock())
+
+    def test_clear_elements(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_iphuuM6Weec6oohooxug',
+            'test_key_bi7ur1UoB1eehiloh7mi': 'test_value_jieTh6aiwoo8eig1AeSa'}]
+        request = MagicMock()
+        self.viewset.request = request
+        self.viewset.clear_elements(request=request, pk=MagicMock())
+        self.assertEqual(len(mock_object.return_value.config), 0)
+
+    def test_clear_elements_with_stable(self, mock_object):
+        mock_object.return_value.config = [{
+            'name': 'test_projector_element_6oohooxugiphuuM6Weec',
+            'test_key_bi7B1eehiloh7miur1Uo': 'test_value_jiSaeTh6aiwoo8eig1Ae',
+            'stable': True}]
+        request = MagicMock()
+        self.viewset.request = request
+        self.viewset.clear_elements(request=request, pk=MagicMock())
+        self.assertEqual(len(mock_object.return_value.config), 1)