AT&T System 25 - Manual (Page 248)

MAINTENANCE
Overheating Trouble
A clogged or dirty air filter can cause the cabinet to overheat. The cabinet air
filter rests on the floor of the cabinet under the CP carrier. The air filter
should be inspected on any service call and replaced as needed (with air filter
comcode 845948348).
Caution:
To replace the
Warning:
Check underneath cabinet for paper and other debris
that could clog the air filter and cause the cabinet to
o v e r h e a t .
air filter, pinch it in the center and pull straight out.
To reduce risk of fire, air filter must be in place during
o p e r a t i o n .
Backplane and Cabinet Trouble
The backplane provides power, TDM bus connections, and station and trunk
interconnections. Each carrier has 12 universal slot positions. Any port CP
can be installed in any slot.
Connection to the corresponding stations or
trunks is made through the backplane to the appropriate cross-connect field.
Danger: Hazardous voltages are present on some backplane
pins. Unplug the power cord and wait at least 5 minutes
before removing the rear cover.
Figure 4-9 provides a rear view of the cabinet backplane (rear cover must be
removed). Typical backplane pin designations are noted on Figure 4-9 for
pins 355, 254, and 056 located on slots 4, 3, and 1, respectively. Address
plug locations for Cabinets 1, 2, and 3 are also noted. The address plug
position assigned slot 8 is reserved for future use. Seven leads (BAO through
BA6, see Figure 4-10) are tied to corresponding logic levels to uniquely
identify each CP slot in the system, including multiple cabinet systems. The
logic values on leads BA4 and BA5 are used to identify the cabinet (Cabinet
1, 2, or 3) and are tied through the cabinet address plugs to either +5 V dc or
ground, as appropriate. Lead BA6 is tied to ground.
An address plug inserted on a cabinet’s backplane (pins 19 and 20) at slot 5
designates the cabinet as Cabinet 1, slot 6 = Cabinet 2, and slot 7 = Cabinet
3.
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