363-206-285
Shelf Descriptions and Configurations
3-6 Issue 3 June 2001
As shown in Figure 3-1, starting at the far left, two 4-inch slots are reserved for
service and protection timing circuit packs (TG).
The next two 8-inch slots are reserved for service and protection main dual OC-1,
OC-3, IS-3 or OC-12 OLIU circuit packs.
The following six 8-inch slots are for the function units. These slots are divided in
three groups designated A, B, and C. The function unit slots can be equipped,
depending on the application, with DS3, TMUX, MXRVO, EC-1 or OC-1 or OC-3
OLIU circuit packs.
The next section of the shelf is reserved for the DS1 low-speed interface or HDSL
circuit packs. These slots are also divided into three groups designated A, B, and
C which correspond to the function unit groups. Each group consists of eight 4-
inch slots for service and optional protection DS1 circuit packs (1x7 protected).
Unused low-speed interface slots within a partially equipped group must be
equipped with retainer cards (177A retainer) if DS1 protection is used.
The next section of the shelf consists of two 8-inch slots reserved for control
circuit packs. The auxiliary control slot is reserved for a required overhead
controller (OHCTL) circuit pack. The system controller (SYSCTL) slot is reserved
for the SYSCTL circuit pack.
The user panel, mounted on the right side of the shelf, consists of the following:
■Two −48 volt fuses (5A)
â– Four alarm LEDs
â– ACO/TEST pushbutton control
â– Four (five on Group 4 shelves) status LEDs
â– CIT port
â– Electrostatic discharge (ESD) jack.
Accidental insertion of same-size circuit packs in incorrect slots is prevented
through circuit pack keying. Three keying combinations are provided. The key
mechanism is located on the faceplate latch, with an interference mechanism on
the shelf.
As shown in Figure 3-3, the front of the shelf is covered with an electromagnetic
compatibility (EMC) cover. If the shelf needs to be accessed for maintenance
activities, the cover is hinged to drop down 180 degrees, or it can be easily
removed by pulling out when at 45 degrees. The back of the shelf is covered by
an inner cover over the DS1 interface connectors and an outer cover over the rear
of the shelf. All covers are necessary to meet the EMC guidelines set by the
Federal Communications Commission (FCC).
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