Figure 49: Dc Power Supply Module; Table 34: Dip Switch Positions On The Dc Psm - Juniper MX2020 Hardware Manual

Copyright © 2015, Juniper Networks, Inc.
NOTE: The MX2020 systems configured for DC input power must use only
DC PDMs and DC PSMs. AC and DC PSMs or PDMs must not be mixed within
a single system.
Up to nine PSMs may be connected in parallel to increase available system power across
MPCs as needed and provide redundancy.

Figure 49: DC Power Supply Module

The DC power subsystem is feed redundant. Each DC PSM can be connected to two
separate feeds from different sources that are used to provide feed redundancy. If two
feeds are connected, PSM input power will be drawn from the feed with the higher voltage
present. There are two PDMs per power subsystem capable of carrying nine feeds each.
Connect feeds from one source to one PDM and feeds from the other source to the second
PDM of the power subsystem. The primary input of the PSM is a dual redundant feed,
and . Both feeds are active during operation, but both feeds may or may not
INP0 INP1
be providing current. Move the input mode DIP switch to the on or off position to determine
the power supply feeds (see
a PSM failure triggers the alarm LED on the craft interface. Each PDM has an LED per
feed indicating whether the feed is active or not, or whether the feed is connected properly,
see "MX2020 DC Power Subsystem Electrical Specifications" on page

Table 34: DIP Switch Positions on the DC PSM

Left Switch Position
Off
On
Off
On
Figure 49 on page
Table 34 on page 97 and
Right Switch Position
Off
Off
On
On
Chapter 9: Power Subsystem
97) shows the DC PSM.
Figure 50 on page 98). In addition,
179.
Input Source
None
Input 0 ( INP0 )
Input 1 ( INP1 )
Both Input 0 and Input 1
97