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Aircraft
Turn your modem OFF before boarding any aircraft.
•
Use it on the ground only with crew permission.
•
Do not use it in the air.
To prevent possible interference with aircraft systems, Federal Aviation Administration (FAA) regulations
require you to have permission from a crew member to use your modem while the aircraft is on the ground.
To prevent interference with cellular systems, local RF regulations prohibit using your modem while
airborne.
Handling Precautions
All devices must be handled with certain precautions to avoid damage due to the accumulation of static
charge. Although input protection circuitry has been incorporated into the devices to minimize the effect of
this static buildup, proper precautions should be taken to avoid exposure to electrostatic discharge during
handling and mounting.
Electromagnetic Interference (EMI) Considerations
The following guidelines are offered to specifically help minimize EMI generation. Some of these guidelines
are the same as, or similar to, the general guidelines but are mentioned again to reinforce their importance.
In order to minimize the contribution of the SocketModem-based design to EMI, the designer must
understand the major sources of EMI and how to reduce them to acceptable levels.
1.
Keep traces carrying high frequency signals as short as possible.
2.
Provide a good ground plane or grid. In some cases, a multilayer board may be required with full layers
for ground and power distribution.
3.
Decouple power from ground with decoupling capacitors as close to the SocketModem module power
pins as possible.
4.
Eliminate ground loops, which are unexpected current return paths to the power source and ground.
5.
Decouple the telephone line cables at the telephone line jacks. Typically, use a combination of series
inductors, common mode chokes, and shunt capacitors. Methods to decouple telephone lines are
similar to decoupling power lines; however, telephone line decoupling may be more difficult and
deserves additional attention. A commonly used design aid is to place footprints for these components
and populate as necessary during performance/EMI testing and certification.
6.
Decouple the power cord at the power cord interface with decoupling capacitors. Methods to decouple
power lines are similar to decoupling telephone lines.
7.
Locate high frequency circuits in a separate area to minimize capacitive coupling to other circuits.
8.
Locate cables and connectors so as to avoid coupling from high frequency circuits.
9.
Lay out the highest frequency signal traces next to the ground grid.
10.
If a multilayer board design is used, make no cuts in the ground or power planes and be sure the
ground plane covers all traces.
11.
Minimize the number of through-hole connections on traces carrying high frequency signals.
12.
Avoid right angle turns on high frequency traces. Forty-five degree corners are good; however, radius
turns are better.
13.
On 2-layer boards with no ground grid, provide a shadow ground trace on the opposite side of the board
to traces carrying high frequency signals. This will be effective as a high frequency ground return if it is
three times the width of the signal traces.
14.
Distribute high frequency signals continuously on a single trace rather than several traces radiating from
one point.
Driving
Check the laws and the regulations regarding the use of cellular devices in the area where you have to drive
as you must comply with these laws and regulations. When using your modem while driving, please give full
attention to driving. Pull off the road and park before making or answering a call if driving conditions so
require.
Children
Do not allow children to play with your modem. It is not a toy. Children could hurt themselves or others (by
poking themselves or others in the eye with the antenna, for example). Children could damage the modem
or make calls that increase your modem bills.
Blasting Areas
To avoid interfering with blasting operations, turn your unit OFF when in a "blasting area" or in areas posted
"turn off two-way radio". Construction crews often use remote control RF devices to set off explosives.
Multi-Tech Systems, Inc. SocketModem EDGE Embedded Wireless Modem Developer's Guide (S000376A)
Chapter 1 – Product Description and Specifications
7
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