All IP Office control units and external expansion modules must be connected to a functional ground. Where the unit is connected to a power outlet using a power cord with an earth lead, the power outlet must be connected to a protective earth.
Use of ground connections reduces the likelihood of problems in most telephony and data systems. This is especially important in buildings where multiple items of equipment are interconnected using long cable runs, for example phone and data networks.
In some cases, such as ground start trunks, in addition to being a protective measure, this is a functional requirement for the equipment to operate. In other cases it may be a locale regulatory requirement and or a necessary protective step, for example areas of high lightning risk.
•
WARNING
During installation do not assume that ground points are correctly connected to ground. Test ground points before relying on them to ground connected equipment.
The ground point on IP Office control units and external expansion modules are marked with a 
or 
symbol. Ground connections to these points should use a 14 AWG solid wire with either a green sleeve for a functional ground or green and yellow sleeve for a protective ground.
•Additional protective equipment
In addition to grounding, additional protective equipment will be required in the following situations. Refer to "Out of Building Telephone Installations".
•On any Digital Station or Phones external expansion module connected to an extension located in another building.
•In the Republic of South Africa, on all Analog Trunk external expansion modules (ATM16) and on any control units containing an analog trunk cards (ATM4/ATM4U).