3.2.3 Frame Ground Connection
1. Loosen the screw.
2. Insert a grounding wire (user-supplied).
3. Tighten the screw.
4. Connect the grounding wire to ground.
Screw
Grounding wire
To ground
WARNING
•Proper grounding (connection to ground) is very important to reduce the risk to the user of
electrocution or to protect the PBX from the bad effects of external noise in the case of a
lightning strike.
•The grounding wire of the AC cable has an effect against external noise and lightning strikes,
but it may not be enough to protect the PBX. A permanent connection between ground and the
ground terminal of the PBX must be made.
CAUTION
For grounding wire, green-and-yellow insulation is required, and the cross-sectional area of the conductor
must be more than 0.75 mm2 or 18 AWG.
Notice
Be sure to comply with applicable local regulations (e.g., laws, guidelines).
In most of the continental United States, the ground provided by the "Third wire ground" at the commercial
power outlet will be satisfactory. However, in a small percentage of cases this ground may be installed
incorrectly. Therefore, the following test procedure should be performed.

Test Procedure

1. Obtain a suitable voltmeter and set it for a possible reading of up to 250 V AC.
2. Connect the meter probes between the 2 main AC voltage points on the wall outlet. The reading obtained
should be 108 V AC to 132 V AC.
3. Move one of the meter probes to the 3rd prong terminal (GND).
Either the same reading or a reading of 0 volt should be obtained.
4. If a reading of 0 volt at one terminal and a reading of 108 V AC to 132 V AC at the other terminal is not
obtained, the outlet is not properly grounded.
This condition should be corrected by a qualified electrician (per article 250 of the National Electrical Code).
5. If a reading of 0 volt at one terminal and a reading of 108 V AC to 132 V AC at the other terminal is obtained,
then set the meter to the "OHMS/RX1" scale, place one probe at the GND Terminal and the other probe
at the terminal which gave a reading of 0 volt.
A reading of less than 1 ohm should be obtained. If the reading is not obtained, the outlet is not adequately
grounded. See qualified electrician.
50 Installation Manual Document Version 2011-10
3.2.3 Frame Ground Connection