User's Manual

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Users should consider the choice of the supplementary services described in section
2.3.2Short Message Service, page 16.
7.4.2 How to Install the Wireless modem
7.4.2.1 Power Supply
Use a high-quality power supply cable with low resistance. This ensures that the
voltages at the connector pins are within the allowed range, even during the
maximum peak current. An electrolytic capacitor should be placed close to the power
supply pins of the wireless modem to supply the peak currents during burst
transmission. See 5.6 Regulated Power Supply Input (VCC), page 38.
7.4.2.2 Grounds
A ground connection is provided at the mounting hole next to the RF connector on
the wireless modem (see Figure 5.1, page 19). Connect this ground point to the GND
pins of the wireless modem by the shortest, low impedance path possible. The
purpose of this connection is to allow any ESD picked up by the antenna to bypass the
wireless modem’s internal ground path.
Note! It is recommended that you use a cable with a maximum resistance of 5
milliohm for the ground connection.
Note! AREF and GND are connected at a single point inside the wireless modem. They
must not be joined together in your application.
7.4.2.3 Audio
Use a coupling capacitor in AUXI line if the application does not use the wireless
modem’s bias voltage. See also Figure 5.10-1 Microphone connections to the
wireless modem, page 54.