+----+               +-------------------+        
| DL |<--+           | RT-11             |
+----+    \          | Monitor           |
           \         +---------------+   |     +--------------+
+----+      \        | RT-11         |   |     | User Program |
| DZ |<------+------>| Multiterminal |<--+---->|     or       |
+----+      /        | Services      |   |     |   Keyboard   |
           /         +---------------+   |     |   Monitor    |
+----+    /          |                   |     +--------------+ 
| DH |<--+           |                   |
+----+               +-------------------+