AL3A-RM User Guide Version B
Document Number: 451-93156-002B
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internal power-on-reset circuit requires two seconds for voltages to decay. Do not reapply
power until this time has elapsed. If the two-second wait time is not adhered to, the reset
circuit may not operate and the A3LA-RM could be placed in a nonoperational state. The state
is not permanent and can be rectified by the above procedure.
The A3LA-RM automatically turns on/off when external DC power is applied/removed via the
EXT_B+ and EXT_GND inputs. The EXT_ON_OFF (pin 1) control input is used to turn a powered
A3LA-RM on and off in a toggle fashion. The EXT_ON_OFF control input is normally “floating”
(i.e., high). When it is pulled to GND level (i.e., low) for at least 270 ms and released, the A3LA-
RM alternates from its current on/off state. The current drawn on the external load used to pull
the A3LA-RM to GND is no more than 0.5 mA. The signal on pin 1 is considered GND when it is
at 0.5 V or less.
2.5
A
UDIO
I
NTERFACE
The A3LA-RM supports both digital and analog audio Input/output (I/O). The digital audio is in
PCM format. In such format, digital audio cannot travel far (less than one foot); this is why the
analog is chosen for the A3LA-RM audio handset. The analog audio input is a single-ended,
unbalanced input with a minimum impedance of 10 kΩ to ground. The A3LA-RM accepts a
maximum input level of 2.0 V peak-to-peak without signal distortion. The analog audio output is
also a single-ended, unbalanced output capable of driving an impedance of 600 Ω or more to
ground. The A3LA-RM delivers undistorted audio up to 2.0 V peak-to-peak.
The combined analog I/O audio interface (pins 5 and 15) and the DPL UART I/O interface (pins
18 and 20) enable an analog audio handset to be connected to the A3LA-RM. With the DPL
audio handset model DPLS0401-X and DB25 data kit model HRC-24-8R, the A3LA-RM can be
used both as a data modem and a satellite phone. This setup, as shown in
, can be an
extremely useful developmental tool because the modem status can be seen on the handset
Liquid-crystal display (LCD) similar to a 9555 Iridium phone.
