User manual

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3.2 Switching OFF the modem
There are two ways to switch off (power down) the modem as described below:
 use the AT#SHDN command; DTR permanently to low (0,8V)
 HR_IN to high level for 1s < t < 2s
A delay of up to 10s is experienced as the modem logs off the network
3.3 Operating states / LEDs
3.3.1 Power up LED (green LED in the middle)
The modem has a green power up LED, as depicted below, which is used to indicate various
operating states. These states are described in following table.
Operating state of GT864-QUAD/PY Terminal
Power up LED state
Device off
Permanently off
net search / not registered /
Fast blinking (period=1s, LED
on
=0,5s
registered full service
Slow blinking (period=3s, LED
on
=0,3s
A call is active
Permanently on
Table 8: Operating states of the power up LED
3.3.2 Status LEDs (one yellow, one red)
The red and yellow Status LEDs are under control of GPIO1 and GPIO2 of the GT864-QUAD/PY
modem inside of the Terminal. They can be controlled via at-commands. The default status of
these two LEDs is off. The following commands have to be used to initialise and to configure
the GPIOs to control the two LEDs:
Switching on GPIO1 at#gpio=1,1,1
Switching off GPIO1 at#gpio=1,0,1
Switching on GPIO2 at#gpio=2,1,1
Switching off GPIO2 at#gpio=2,0,1
These LEDs can be controlled e.g. by an external microcontroller via at-commands issued to
the terminal via the serial RS232 interface. They can be used for signalling any useful status of
the external application such as:
 error indication
 status of communication (GPRS, SMS, CSD, etc.)
 status of GSM-network (to simulate GSM LED)
 quality of service