This guide is a general outline for network troubleshooting for users of the North Carolina Information Highway DS-1 video service. It should be noted that many sites have unique hardware, software and operational setups; thus, some of the following documentation may not apply to your site. Please contact your integrator or NCIH regional coordinator for further clarification, explanation, or documentation related to your specific configuration.

Part I. Hardware

NCIH site facilitators/operators should locate and familiarize themselves with the following equipment and cabling:

1. The telephone company’s demarcation, or demarc. This is a square or rectangular box, up to the size of a videocassette, usually mounted on the wall of your facility or control room within a few feet of the equipment cabinet. Some demarcs have interior light indicators (LEDs), which are normally green. The demarc terminates the telephone company’s DS-1 cable, which is plugged into it. Everything "downstream" (that is, on your side of the box) is a local responsibility. The box itself and everything "upstream" are the telco’s responsibility.
2. Cisco 3810 ATM multiplexer (mux), with built-in data router. The mux is the network interface for the video connection. Data also runs through this box if your site has combined ATM video and data connectivity. It is normally rack-mounted in the video equipment cabinet. There are two ports on the rear panel, which may have been installed facing the front of the cabinet. Locate the T1/E1 (video) port and observe the LEDs. A functional site will have green lights associated with this port. Locate the Ethernet (data) port. This is the interface for LAN connectivity if your site has enabled this service.
3. A Category (CAT) 5 cable connects the demarc to the Cisco 3810. This cable has standard RJ-45 male termination connectors on each end. One end plugs into the demarc and the other connects to the T1/E1 port on the Cisco 3810. If the demarc and equipment cabinet are close together, this cable will be only a few feet long. If the demarc is in a different room, the cable may be considerably longer.
4. The V.35 cable, normally bluish green in color, links the Cisco 3810 to the CODEC. The Cisco end connects to the Serial 0 Port and the other end is connected to the site's codec. Locate the LED associated with the Serial 0 port on the Cisco 3810. When the codec is turned on and is recognized by the mux, this LED will be green.
   For VTEL CODEC sites ONLY, the V.35 cable is also known as the DDM cable. The DDM cable has four spliced connections on the CODEC end, only one of which is used to connect to the codec. The VTEL interface is labeled "V.35 Cable A" and is plugged into the DDM port on the codec. The other three spliced cables are not used.
5. The CODEC is a hardware component that includes special software used to run video sessions. The codec is usually mounted on a shelf in the equipment cabinet. Each site should be provided with the System Administrator or Users Guide. Please familiarize yourself with system overview, operation, and troubleshooting, or visit the manufacturer's web page for more product information. It is essential that NCIH site personnel be familiar with the various user interfaces and icons associated with the codec and also be comfortable with operation and troubleshooting of the unit.
   For VTEL CODEC sites ONLY, a VTEL expansion chassis is connected. This is the black box that connects the codec to other room equipment (video switchers, audio mixers, etc.)through multiple audio and video cables. Typical cabling and connectivity schematics for NCIH equipment packages are provided on the NCIH home page
6. Room monitors, cameras and speakers. Locate these components and become familiar with their setup and proper operation. Depending on the way your facility has been configured, some monitors may show the incoming network video and others may show local site video. The number and use of cameras varies from facility to facility. You should understand the relationship between "teacher," "student," and "document" cameras. In addition, you should know how to activate and route the signals from your VCR if your site is equipped with one.

Part II. Basic Troubleshooting

This section assumes that you are familiar with the hardware, software, and functionalities described in Part I.

The basic tool for network troubleshooting is the loopback plug. This device is a male RJ-45 connector with cabling that, when plugged into a port, "loops" the outgoing or incoming audio- video signals back on themselves. Each NCIH site is provided with a loopback plug upon certification to the network. It is your responsibility to keep it available and to replace it if it is lost or damaged. Your integrator or coordinator can advise you on obtaining a replacement.

The basic network troubleshooting test is the loopback, which determines whether the signal is getting through each piece of network equipment and, consequently, where the problem is localized and whose responsibility it is to fix. There are three kinds of loopback tests: the internal codec loopback, Cisco loopback, and network/circuit loopback. The NCIH Help Desk can assist you with the process and help assess the results, but you are responsible for sufficient familiarity with the system to be able to conduct the tests. The NCIH Help Desk toll-free customer service telephone number is 800-441-5296.

This test verifies that the codec system and expansion chassis (if applicable) are working properly and that signal transmission/reception is being accomplished within the codec. It is conducted using the CODEC software and may only be performed when NOT connected in a video session. The loopback plug is not needed. Please consult the CODEC's System Administrator or Users Guide for instructions on how to conduct this test.

Running a Cisco Loopback

This test verifies that the Cisco 3810 is receiving the signal from the codec and processing the information properly. It is performed using the loopback plug. You must connect the codec for this test to work.

• Disconnect the CAT 5 cable from the T1/E1 port on the Cisco 3810.
• Insert the loopback plug into the T1/E1 port.
• Make sure a valid video source to send/transmit has been selected.
• Place a call ffrom the codec
• When the connection has been made, the local video source should be visible on the incoming video monitor. Create some motion by waving your arms, walking around the room, etc. The video signal will be noticeably delayed and you will hear echo.
• Remove the loopback plug and reconnect the CAT 5 cable to the T1/E1 port. If a session is in progress, the incoming video signal should be restored. If a session is not in progress, you may see either a gray screen or a frozen image of the local video source.

This test verifies that there is no problem with the DS-1 circuit or NCIH network configuration. It can be done only in cooperation with the site's local telephone company and will generally be done only at their request. It requires the use of the loopback plug. To conduct this test:

• Disconnect the CAT 5 cable from the demarcation box.
• Insert the loopback plug into the CAT 5 port on the demarcation box.
• Follow the instructions of the Telco or Help Desk technician.
• When the test has been completed, remove the loopback plug and reconnect the CAT 5 cable.