Positron Teleline 751109/15, Description And Installation

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29
Ground Connections
3.3.1 Powering model 751313MC or 751318MC from an AC
Source
If a Power Supply Card, model 751313MC or 751318MC is used and is powered
from an AC source, the following instructions apply:
1. The preferred way of grounding the shelf is to connect a solid ground to the
shelf ground lug, NOT connecting a ground to TB3-2 and setting W1 to
“CONNECTED” position.
2. If the Station ground lug is used and you are forced to connect the power cord
ground to TB3-2, the ground strap W1 on the Station side motherboard must
be in the “DISCONNECTED” position. This will prevent creating a ground
loop.
3. If a local Station ground is not available and grounding is done through the
power cord ground wire (TB3-2), then ground strap W1 must be in its
“CONNECTED” position. Doing this will connect the station backplane ground
to the power cord ground wire.
For an illustration of the ground strap settings, refer to Figure 3 on page 30.
C
AUTION
Q
Teleline Plug-in Power Supplies are CSA approved. No other power
supply can be used inside a Teleline shelf.
Q
The shelf ground lug is the preferred way to ground the shelf.
Q
The 751313MC and 751318MC input is protected through the power
cord ground wire, but since the ground lug provides better current
carrying capacity, it is the preferred way of grounding the shelf. The
jumper W1 is used to either connect the station backplane ground to the
power cord ground (CONNECTED) or not (DISCONNECTED). If the
ground lug is connected to a solid station ground and W1 is in the
“CONNECTED” position, a ground loop could result and electrical
“hum” could be present on the circuit cards. Therefore, when using the
ground lug, do not connect a ground to TB3-2 and put W1 in the
“CONNECTED” position. If local electrical code state that you must
connect the power cord ground, then you must do so and put W1 in
“DISCONNECTED” position.