Sierra Wireless MP 875 - Manual (Page 60)

MP875 Modem User Guide
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Digital output devices
Digital output devices are those that have only two states and
the state is controlled by a signal from the MP modem. Any
device that is to be switched on and off from 3G Watcher
would be installed as a digital output device.
A digital output can be connected to two of the pins on the
DB15HD connector: Pins 3 and 11. (These can be used for
either input or output.)
Note: Before using the input/output lines, you must configure them as
inputs or outputs.
Typically a digital output device should be connected between
Ground (pin 10) and the output port (Pin 3 or 11).
Figure 6-3: Wiring for using Pin 3 (digital output) as an electronic switch. Pin
10 is Ground.
The digital I/O ports provide open‐collector output to a
maximum of 500 mA.
Analog input devices
Analog input devices are those that generate a signal of
varying voltage, based on the state of an instrument or gauge.
An example of an analog input device might be a sensor that
detects the vehicle’s speed.
An analog input can be connected to four of the pins on the
DB15HD connector: Pins 7, 8, 14, and 15.