2. DPMS
DPMS (Display Power Management Signaling) is a standard to
reduce power consumption in monitors. Typically, both the monitor and the video card
must support the DPMS standard in order to receive any benefit from it. DPMS specifies
four modes of operation (in order of increasing power savings): "Normal", "Standby",
"Suspend" and "Off". Two signal lines, "Horizontal Sync" and "Vertical Sync" provide
a method for signaling these four different states to a DPMS monitor.
A good technical resource on DPMS is available at
http://webpages.charter.net/dperr/dpms.htm.
2.1. Normal
Normal means just that -- the monitor is fully powered and on.
LCD laptop panels and LCD flat screens use considerably less power than traditional CRT
monitors.
2.2. Standby
Standby is used to describe a very minor power
savings level. This setting usually involves
blanking the screen by turning off the electron (RGB) gun. However, the
power supply is left on and the tube filaments energized.
When you need to use the monitor again, the monitor will come back on very
quickly.
This option requires DPMS monitor and video card support along with enabling
DPMS in XFree86.
Standby is sometimes referred to as hsync suspend mode
since the horizontal sync signal
is turned off to signal this power management state to a DPMS monitor.
2.3. Suspend
Suspend is used to describe a very strong low power
state. This setting usually involves the same
power conservation as Standby however in addition the power
supply to the monitor is turned off.
This option requires DPMS monitor and video card support along with enabling
DPMS in XFree86.
Suspend is sometimes referred to as vsync suspend mode
since the vertical sync signal
is turned off to signal this power management state to a DPMS monitor.
2.4. Off
Off usually means just that -- the computer monitor
is turned off. Usually, a small
auxiliary circuit stays on to monitor the signals from the computer to turn
the monitor back on when data needs to be displayed to the screen.
Obviously, this keeps power consumption to a bare minimum (if not zero).
While the power saving is substantial, to reactivate the monitor may take
several seconds.
This option requires DPMS monitor and video card support along with enabling
DPMS in XFree86.
Both the horizontal and vertical sync signals are turned off to signal this
power management state to a DPMS monitor.
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