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M850B   L S I   A ir c r a f t   T im e   M a n a g e m e n t   S y s t e m

Greenwich Mean Time

Local Time

Flight Time

Elasped Time

CLOCK OPERATION

Normal Operation

The select, SEL, button selects what is to be displayed 
in the four digit window and the Control, CTL, button 
controls what is being displayed. Pressing SEL 
sequentially selects GMT, Local Time, Flight Time, 
Elapsed Time, Count Down Time, and back to GMT. The 
CTL button starts, stops and resets Elapsed Time when 
momentarily pushed. Normal operation of the 850B 
cannot accidentally reset time.

Setting GMT

Select GMT for display in the four digit window with the 
SEL button. Simultaneously press both the SEL and CTL 
buttons to enter the set mode. The tens of hours digit 
will start flashing. The CTL button has full control of the 
flashing digit and each button push increments the digit. 
Once the tens of hour is set, the SEL button selects the 
next digit to be set. After the last digit has been selected 
and set with the CTL button, a final push of the SEL 
button exits the mode. The lighted annunciator will 
resume its normal flashing, indicating the GMT clock is 
running.

Setting LT

Select Local Time, LT, using the SEL button. Simultane-
ously push the SEL and CTL buttons to enter set mode. 
The tens of hours digit will start flashing. The set 
operation is the same as for GMT, except that minutes 
are already synchronized with the GMT clock.  Minutes 
can be changed in 15 minute increments for special 
time zones.

Setting Flight Time Alarm

When Flight Time, FT, is displayed enter the set mode by 
pressing both buttons simultaneously. The alarm time is 
entered identically to GMT setting. When the Flight Time 
equals the alarm the display will flash and the alarm 
output is activated. If FT was not being displayed at the 
time the alarm becomes active, the clock automatically 
selects FT for display. Pressing either the SEL or CTL 
button turns off the alarm. Flight Time is unchanged and 
continues counting.

Flight Time Reset

FT must be displayed when resetting. Hold CTL down for 
3 seconds or until 99:59 or 99:99 appear on the 
display; Flight Time will be zeroed upon the release of 
the CTL button. The digits that appear (99:59 or 99:99) 
depend on how the clock is programmed - in hours and 
minutes or in hours, tenths, and hundredths.

Elapsed Time

Select ET for display. Pressing the CTL button will start 
ET counting. Elapsed Time counts up to 59 minutes, 59 
seconds, and then switches to hours and minutes. It 
continues counting up to 99 hours and 59 minutes. 
Pressing the CTL button again stops ET, another press 
resets ET.  ET has a countdown timer function, repeat 
steps for CDT in ET mode.

Count Down Time

Select CDT for display and enter set mode by pressing 
both buttons. The Count Down timer can now be set. 
Entering the time is identical to GMT time setting. When 
the time is entered and the last digit is no longer 
flashing the clock is ready to start the countdown. 
Momentarily pressing the CTL button starts the 
countdown. When count reaches zero the displays flash 
and the external alarm is activated. Pressing either SEL 
or CTL will deactivate the alarm. CDT continues 
counting up. Next press on CTL button to stop counting. 
Second press resets CDT to previous set time.  

Test Mode

In GMT mode, Hold the SEL button down for three 
seconds and the display will indicate 88:88 and activate 
all five annunciators.

FIELD OPTION CHANGES

When changes are made the connector of the clock 
must be grounded to the soldering iron or warranty may 
void.

Local Time:

 

To change from12 hour to 24 hour 

format, hold SEL in LT mode for 5 seconds until12 HR 
(hour) or 24 HR (hour) flashes, then push CTL for 
desired format. Push SEL to exit set mode. 

Flight Time:

 To change from recording in hours, 

minutes to recording in hours, tenths, and hundredths, 
remove case and jumper OPT-99.

Battery:

 

is a CR2032 coin cell. The recommended 

change interval is 5 years. The battery may be removed 
permanently if the aircraft battery is connected to the 
Keep Alive input (Pin 9).  ***Recommend to remove 
CR2032 battery if pin 9 is used.

Backlighting SET-UP: 

Press and hold 

down the SEL button on power up to verify backlighting 
configuration.  Pressing CTL will provide sequence 
options 5(Volt), 14(Volt), 28(Volt), and A (Automatic 
Sensing).  Select backlighting voltage and press SEL 
button to confirm.  A (Automatic Sensing) will provide 
automatic backlighting for  input voltage 14 and 28 Volt.

Download installation manual www.davtron.com product page M850B

Count Down Time

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