Zte S217 User Manual page 10

 To avoid possible interference with blasting operations,
switch off your phone when you are near electrical blasting caps,
in a blasting area, or in areas posted "Turn off electronic
devices." Obey all signs and instructions.
Precautions for Electronic Devices
 Some electronic devices are susceptible to electromagnetic
interference sent by mobile phone if inadequately shielded,
such as electronic system of vehicles. Please consult the
manufacturer of the device before using the phone if necessary.
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