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Cisco MGX 8950 Hardware Installation Guide
Release 3, Part Number 78-14147-02 Rev. A0, November 2002
Chapter 1 Product Overview
System Hardware Components
DC PEM
The Cisco MGX 8950 can accept power from a –48 VDC (–42 + –56 VDC) DC source that connects to
one (primary) or two (secondary/redundant) –48 VDC PEMs. Each primary or redundant DC source
connects to one DC PEM in the system. Each DC PEM accepts two 100 A service feeds from the same
DC source.
Figure 1-34 shows a close-up of the DC PEM.
Figure 1-34 Cisco MGX 8950 DC PEM
For a DC-powered system, the DC PEMs are installed at the back of the air intake plenum. If you install
only one DC PEM, install it on the bottom, as viewed from the rear of the air intake plenum.
(See
Figure 1-35.)
Figure 1-35 Primary and Secondary DC PEMs
For more information about DC power requirements, see the “Power” section on page 2-17.
DC
J2 output
connector
-48V DC
-48V DC 50A
-48V
RTN
J2
J1
-48V DC 50A
-48V
RTN
43978
Circuit breaker
J1 output
connector
DC OK
LED
Plastic
cover
Terminal
block 2
Terminal
block 1
-48V
D
C
50A
DC
D
C
-48V
D
C
50A
-48V
R
T
N
J2
J1
-48V
D
C
50A
-48V
R
TN
-48V D
C 50A
-48V
D
C
50A
-48V
R
TN
J2
J1
-48V
D
C
50A
-48V
R
TN
43975
Secondary PEM
Primary PEM