Specifications

Common Equipment Description 2-9
Cooling Assemblies
DC Power Drain and Circuit Protection
Each card in an MGX 8220 shelf draws an average of 21 watts with a worst case shelf current of
14.40 amps.
The circuit breaker in the DC Power Entry Module (PEM) is rated at 15.00 amps.
The MGX 8220 circuits are protected as follows:
• The backplane has a 5 amp fast blow fuse for each slot position.
• Each board has a 1.5 amp circuit breaker in the -48 VDC line to the DC/DC converter.
Each MGX 8220 board is equipped with a DC/DC converter (Shindengen—HGG05006 or
AT&T—JW030A) which has an automatic current limited to 5 volts output.
A schematic of the DC power system is shown in Figure2-8.
Figure2-8 DC Power System
Cooling Assemblies
The MGX 8220 cooling assembly consists of multiple rack-mounted units:
• main cooling assembly
• booster cooling assembly
• plenum exhaust chamber
• spacer unit