Returns the signal strength of the device. The values return are:

• OperatorName (Name of the Cell Signal Operator);
• dBM (Signal strength in dBm, which is the signal strength of the pilot signal or equivalent.);
• Asu (Signal strength in Arbitrary Strength Units, calculated from the strength of the pilot signal or equivalent.);
• Level (Abstract level value for the overall signal quality. From 0 to 4.)