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5. Functional Description
The ATX mains unit is equipped with an automatic recognition of the existing mains voltage (115V~/
230V~, 50/60Hz). Thus, incorrect setting of the existing mains voltage is prevented.
The ATX mains unit converts this mains voltage in the direct voltages (+5V=, +12V=, -12V= and
3.3V=) internally required by the computer.
An integrated fan dissipates excess heat arising from this conversion outwards.
The ATX mains unit can be switched on/off by means of the mains switch.
Nevertheles, the computer does not start when the mains switch is switched on. First,
both mains unit and the connected mainboard are in the so-called “Standby” mode. To
start the computer, press the Power key at the front of the ATX housing. The key must
be connected to the respective connection on the mainboard (e.g. connection “ATX
Power” or similar, see manual of the mainboard) via a cable.
When you switch off your computer by means of the Power key, there still is a standby
voltage applied to your mainboard.
This voltage is necessary e.g. for switching on the computer via the keyboard or the
mouse (provided the BIOS of your computer allows this possibility) or via the automatic
switch-on or boot-up in case of a modem/ISDN call/network access (depending on BIOS,
hardware and software).
Therefore, in case of interventions on your computer (e.g. when installing a new plug-in
board), the ATX mains unit has to be switched off in advance by means of the mains
switch on the ATX mains unit and has to be separated from the mains voltage.
Additionally, always unplug the mains plug! Otherwise, the mainboard and further
components might get damaged!
The mains unit is equipped with a speed output of the internal fan. This one can be connected to an
appropriate connection of your mainboard (speed monitoring e.g. in BIOS).
The speed of the fan integrated in the mains unit can be modified via the speed regulator of the 5.25"
plug-in module (at excessive temperatures inside the mains unit, the speed is increased automatically).
The delivered power is indicated via a display which is integrated into the 5.25" plug-in module.
Nevertheless, this indication is only an approximate value calculated by the internal electronics.
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