Follow these basic guidelines when working with any electrical equipment:
Before beginning any procedure requiring access to the chassis interior, locate the emergency power-off switch for the room in which you are working.
Disconnect all power and external cables before moving a chassis.
Do not work alone in potentially hazardous conditions.
Never assume that power has been disconnected from a circuit; always check.
Do not perform any action that creates a potential hazard to people or makes the equipment unsafe; carefully examine your work area for possible hazards such as moist floors, ungrounded power extension cables, and missing safety grounds.
Telephone Wiring Guidelines
Use the following guidelines when working with any equipment that is connected to telephone wiring or to other network cabling:
Never install telephone wiring during a lightning storm.
Never install telephone jacks in wet locations unless the jack is specifically designed for wet locations.
Never touch uninsulated telephone wires or terminals unless the telephone line has been disconnected at the network interface.
Use caution when installing or modifying telephone lines.
Preventing Electrostatic Discharge Damage
Electrostatic discharge (ESD) damage, which can occur when electronic cards or components are improperly handled, results in complete or intermittent failures. SIPs, SPAs, and processor modules comprise printed circuit boards that are fixed in metal carriers. Electromagnetic interference (EMI) shielding and connectors are integral components of the carrier. Although the metal carrier helps to protect the board from ESD, use a preventive antistatic strap during handling.
Follow these guidelines for preventing ESD damage:
Always use an ESD wrist or ankle strap and ensure that it makes good skin contact.
Connect the equipment end of the strap to an unfinished chassis surface.
When installing a component, use any available ejector levers or captive installation screws to properly seat the bus connectors in the backplane or midplane. These devices prevent accidental removal, provide proper grounding for the system, and help to ensure that bus connectors are properly seated.
When removing a component, use any available ejector levers or captive installation screws to release the bus connectors from the backplane or midplane.
Handle carriers by available handles or edges only; avoid touching the printed circuit boards or connectors.
Place a removed board component-side-up on an antistatic surface or in a static shielding container. If you plan to return the component to the factory, immediately place it in a static shielding container.
Avoid contact between the printed circuit boards and clothing. The wrist strap only protects components from ESD voltages on the body; ESD voltages on clothing can still cause damage.
Never attempt to remove the printed circuit board from the metal carrier.
For safety, periodically check the resistance value of the antistatic strap. The measurement should be between 1 and 10 megohms (Mohms).
An optical single-mode transmitter uses a small laser to transmit the light signal to the network. Keep the transmit port covered whenever a cable is not connected to it. Although multimode transceivers typically use LEDs for transmission, it is good practice to keep open ports covered and avoid staring into open ports or apertures.
The following warnings apply to SPAs and SFP modules that transmit signals through an optical carrier signal:
The single-mode aperture port contains a laser warning label.
Figure 1. Class 1 Laser Warning Labels for Single-Mode Port
The multimode aperture contains a Class 1 LED warning label.
Figure 2. Class 1 LED Warning Labels for Multimode Port