Service Manual
GSM-204-323
Horizonmacro outdoor temperature control
31st Oct 01
Technical Description: Horizon
macro
outdoor
68P02902W02-A
CONTROLLED INTRODUCTION
Tech. 3–1
Horizon
macro
outdoor temperature control
Temperature
control
overview
The Horizon
macro
outdoor cabinet contains equipment that has to be
maintained within the operational temperature range to ensure correct operation
of the equipment, and to guard against premature failure of the individual
components.
Cabinet over
temperature
control
Under overheat conditions, as the temperature rises above preset levels,
temperature sensors located in various areas within the cabinet provide alarms.
A further increase in temperature causes sensors, set at higher temperature
thresholds, to initiate PSM or cabinet shutdown. The cabinet is restarted when
the sensors are reset by a substantial fall in temperature.
TOPSMs and CTUs have their own internal total shutdown responses to
overheating. The CTUs shutdown at 92 C.
850/900 MHz CTUs also have an internal 4 dB power reduction shutdown
response to overheating, at 85 C. 1800/1900 MHz CTUs have a 0.6 dB cut
back at 70 C in addition to the 4 dB power reduction at 85 C.
Both the CTU and TOPSM shutdowns provide a second level of cabinet
protection, independent of the cabinet heat sensors.
Temperature
sensors
Radio enclosure temperature sensors
Temperature sensors are located above the transceiver compartment (see Cage
backplane interface panel harness assembly Figure 2-9) and consist of the
following:
One 70 C sensor, providing sensing for a cabinet overtemperature alarm
when the EMC enclosure temperature exceeds the preset level. The alarm
is processed by the alarm module and the MCUF, and sent on to the
OMC-R, via the BSC.
Two 85 C sensors initiate shutdown of the PSMs to protect the cabinet
equipment from heat damage. Both sensors must detect excess
temperature for the shutdown to take place; this reduces the risk of an
unnecessary shutdown due to sensor failure. If a shutdown occurs, there
is no prior notification to the OMC-R.