IC Realtime 1/2/4 Channel H.264 Network Video Server - Manual (Page 98)

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 The monitor system usually can adopt the one-point ground.
 Please connect the ground end of 3-pin socket in the monitor system to the ground port of
the system (protection ground cable)
4. The shortcut way to check the electric system using the digital multimeter
For 220V AC socket, from the top to the bottom, E (ground cable), N (neutral cable), L(live cable).
Please refer to the following figure.
There is a shortcut way to check these thee cables connection are standard or not (not the
accurate check).
Importance
In the following operations, the multimeter range shall be at 750V!
For E (earth cable)
Turn the digital multimeter to 750V AC, use your one hand to hold the metal end, and then the
other hand insert the pen to the E port of the socket. See the following figure. If the multimeter
shows 0, then you can see current earth cable connection is standard. If the value is more than
10, then you can see there is inductive current and the earth cable connection is not proper.