Observing Operations | Reviews | Survey Management

Accessing the Interlock System Graphical Display from an X-terminal

William N. Boroski
Fermi National Accelerator Laboratory

This document descibes the procedure for bringing up the 2.5-meter telescope interlock system graphical display in an X-window.  Permission to log onto the SDSS computer system, sdsshost.apo.nmsu.edu, is required.

An interlock system has been implemented on the SDSS 2.5-meter telescope to protect the telescope and its instruments from damage due to inadvertent actions.  This system is designed to provide equipment protection.  It is not a human safety interlock system.

The interlock system design and implementation is explained using logic diagrams, which are located in hard-copy form in a binder near the telescope.  Users of the telescope should make themselves familiar with these diagrams.  In addition to the hard copy diagrams, a graphical display  has been developed to make it faster and easier to view the state of the system and aid in diagnosing interlock trips.  The display, which can be opened in an X-window, begins with a high-level view of the interlock system status.  Clicking on the various elements allows one to move deeper into the system logic.  Green elements indicate clear conditions; red elements indicate an interlock that is in a tripped state.  By moving through the logic, the user can quickly traverse the interlock system to find an interlock that has been tripped or is otherwise preventing the desired action.

This procedure will instruct users in how to access the interlock display.  Questions regarding the design and operation of the interlock system should be addressed to John Anderson, Glenn Federwitz, or Paul Czarapata.  Questions regarding the design and implementation of the interlock graphical display should be addressed to Robert Lupton or Dennis Nicklaus.


  1. Log onto sdsshost.apo.nmsu.edu through an ssh session.  If you do not have an account, contact the APO Systems Adminstrator, Craig Loomis.

  2. If you are logging in from a PC, you must have X-software running before continuing, but you do not need to start an X-session.  For example, if you have Exceed installed on your machine, start Exceed, but don't worry about logging into a host machine. The interlock display tools will open the necessary X-windows for you.

  3. If you are logging in from a PC, it will be necessary to have the video output mapped to your terminal.  If this has not already been done, type the following command at the prompt:
    1. export DISPLAY=IP address:0     //where IP address is the address of your machine
    Note that the operating system  is case sensitive.

  4. From the command prompt, type setup interlocks.

  5. When the prompt returns, type interlocks.  This will bring up the interlocks graphical display in an X-window. Be patient, as it may take a little while to load.

  6. To exit the program, click on the Exit button.

Last modified 09/30/99

Submit comments and questions to the SDSS Helpdesk. Last updated 10/31/08