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Connect Power to a DC Router
Table 1: DC Power
System Input Voltage
DC input voltage
Operating range: –40.0 to –72 VDC
Note: If the input voltage from the DC power source drops below -37.5 to -39.5
VDC, the routing platform automatically shuts down. During automatic shutdown,
the circuit remains active. When the input voltage returns to –43.0
to –44.00 VDC, the router automatically starts up again and the system
returns to normal operation within 30 minutes. No operator intervention is
Figure 7: Connect Ground and Power Cables
Ensure that the voltage across the DC power source cable leads is 0 V
and that there is no chance that the cable leads might become active during
Caution: You must ensure that power connections maintain the proper polarity.
The power source cables might be labeled (+) and (–) to
indicate their polarity. There is no standard color coding for DC power cables.
The color coding used by the external DC power source at your site determines
the color coding for the leads on the power cables that attach to the terminal
studs on each power supply.
- Attach an electrostatic
discharge (ESD) grounding strap to your bare wrist and connect the strap to
an approved site ESD grounding point. See the M120 Internet Router Hardware Guide.
the grounding cable to a proper earth ground.
- Verify that a licensed electrician has attached the cable
lug provided with the router to the grounding cable.
Place the grounding cable lug over the grounding points on the bottom
rear of the chassis. The left pair is sized for M6 bolts, and the right pair is sized for UNC 1/4-20 bolts.
- Secure the grounding cable lug to the grounding points,
first with the washers, then with the screws.
- Verify that the source
power cabling and the grounding cabling are correct, that they are not touching
or blocking access to router components, and that they do not drape
where people could trip on them.
Switch the circuit breaker on the power supply faceplate to the off
- Remove the clear plastic cover protecting the terminal studs on the faceplate.
- Attach the power cable lugs to the terminal studs on the power
supply faceplate. Secure the power cable lugs to the terminal studs, first
with the flat washer, then with the nut. Apply between 12 lb-in. (1.4 Nm)
and 15 lb-in. (1.7 Nm) of torque to each nut.
- Attach the positive (+) DC source power cable lug to the RETURN (return)
- Attach the negative (–) DC source power cable lug to the –48V (input)
Note: For information about connecting to DC power sources, see the M120 Internet Router Hardware Guide.
- Loosen the captive screw on the cable restraint on the lower edge of the power supply faceplate.
Route the positive and negative DC power cables through the top and bottom of the cable restraint.
- Tighten the cable restraint captive screw to hold the power cables in place.
- Replace the clear plastic cover over the terminal studs on the faceplate.
- Verify that the ground and power cabling are correct, that
they are not touching or blocking access to router components, and
that they do not drape where people could trip on them.
- Switch on the external circuit breakers to provide voltage to
the DC power source cable leads.
Proceed to 6: Perform Initial Software Configuration.
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