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3.8 FMU
3.8.1 Functions
The FMU is located in the fan box. It manages and controls fans in the fan box to guarantee
satisfactory heat dissipation of the BTS.
The FMU has the following functions:
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!
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3.8.2 DIP Switch
Figure 3-22
Figure 3-22 FMU layout
The FMU is applicable to multiple types of the BTS. It can be installed in a big or a small fan
frame in the cabinet. The data cable of the big fan is connected to J1 on the FMU, and the
small one is connected to J8–J11 (their designations are FAN1–FAN4).
J5 and J6 are used only for the cascading of the BTS30. J5 is the input socket, and J6 is the
output socket. For the BTS in the cascade network, when the BTS30 is cascaded, the J6 on the
FMU of the lower level BTS30 is connected to J5 on the FMU of the upper level BTS30 to
realize the transmission of power signals and alarm signals.
3-30
Feeding fans
This part of circuit consists of two devices: power supply filter and voltage reduction. It
processes the working power needed from system power supply to fans, and provides
feeding to the fan.
Controlling the fan speed
The voltage-control mode is used to control the fan speed. The rotation is maintained at a
constant speed within the variation range of voltage to dissipate heat.
Monitoring alarms
Two types of fan failure are stalled circuited and short circuited. The symptom of these
two cases is that the fan stops running. The FMU monitors the speed of the fan to decide
the working status of the fan. If the fan is faulty, the alarm signals are sent to the PMU.
shows the FMU layout.
J1
J6
Huawei Technologies Proprietary
M900/M1800 BTS3X Series Base Transceiver Station
J8
J9
J10
J11
FAN1
FAN2
FAN3
FAN4
S1
Hardware Description Manual
J5
ON
Issue 01 (2006-11-18)
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