3. Determine if the transmitter
unit is beyond a limited range
of communications
Transmit a signal to the control unit
from the transmitter unit
Selectively generate an
alert at the control unit
Yes
Receive a signal from a control
unit at a transmitter unit
No
FIG. 2
210
220
230
240
6. User turns on power
Read battery voltage
Display batter low
warning on the LCD
Wait 20 seconds
Display battery level
on the LCD
Wait for initialization
message from the
transmitter unit
Is the
battery level
OK?
Was a message
received with a
correct identifier?
Send acknowledge
message with a delay
parameter D1
Stop the buzzer alarm,
clear the warning on
the LCD, and set the
LED green
Display battery level
on the LCD
Is the
battery level
OK?
Wait (D1 + 2) seconds
for an alive message
from the transmitter unit
Was a message
received with a
correct identifier within
(D1+2) seconds?
Was the
message an
alive
message?
Send an acknowledge
message
Yes
No
Yes
Yes
Yes
Yes
No
Sound the buzzer
alarm, set a warning
on the LCD, and set
the LED red
Read battery voltage
No
No
No
FIG. 4A
401
402
403
404
406
405
407
408
409
410
411
412
413
416
418
417
415
414
7. User turns on power
Read battery voltage
Blink the LED red as a
low battery warning
Wait 20 seconds
Set the LED red
Is the
battery level
OK?
Was an acknowledge
message received?
Yes
No
No
No
FIG. 4B
450
451
452
454
453
455
458
Send an initialization message
with an identifier of the
transmitter unit to the control unit
456
Wait 20 seconds for an
acknowledgement message from the
control unit with a delay parameter D1
457
Store the parameter D1
from the control unit
459
Set the LED green
460
Read battery voltage
Is the
battery level
OK?
461
462
Send an alive message with the identifier of
the transmitter unit to the control unit
Wait D1 seconds for an acknowledge
message from the control unit
Was an acknowledge
message received?
Set the LED green
467
Set the LED red
466
Yes
Yes
Yes
No
463
464
465
