==== dtg_service_attribute_descriptor

Defined by DTG in <<DTG-DBOOK>>.

[source,xml]
----
<dtg_service_attribute_descriptor>
  <!-- One per service -->
  <service service_id="uint16, required"
           numeric_selection="bool, required"
           visible_service="bool, required"/>
</dtg_service_attribute_descriptor>
----
