User guide
Table Of Contents
- Presentation
- Warning
- Copyright
- 1 References
- 2 Packaging
- 3 General presentation
- 4 Characteristics and Services
- 5 Use of the modem
- 5.1 Starting with the modem
- 5.2 Specific recommendations for the use of the modem in vehicles
- 5.3 GSM led of the modem
- 5.4 Echo function of AT commands deactivated
- 5.5 Checking the quality of the GSM reception signal
- 5.6 Verification of PIN code
- 5.7 Verification of modem registration on GSM network
- 5.8 Verification of modem registration on GPRS network
- 5.9 Verification of internal voltages of the modem
- 5.10 Main AT commands (HAYES)
- 5.11 Turning OFF the modem
- 5.12 Updating procedure of the modem
- 6 Trouble Shooting
- 7 Functional description
- 8 Technical characteristics
- 8.1 Mechanical characteristics
- 8.2 Electrical characteristics
- 8.3 Environmental characteristics
- 8.4 Standards/Conformities
- 9 Security recommendations
- 10 Recommended accessories
- 11 Client support
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Descriptions and non-contractual illustrations in this document are given as an indication only.
ERCO & GENER reserves the right to make any modification.
Dct_427_01
8.2.4.1 Microphone
The microphone input is designed for a direct connection of the electret condenser micro. (For more details,
see the command AT+USPM).
By default, the microphone input is active (pins MICP, MICN)
Table 33 : Polarization characteristics for a dynamic microphone
Micro Input
Parameter/Conditions Min Typ Max Units
Microphone supply open circuit
voltage output
Provided by MICP with MICN. 2.2 V
Microphone supply current 2 mA
Microphone supply output
resistance
2.85 3 3.15 k
Microphone ground MICN 0 V
Table 34 : Characteristics recommended for the dynamic Microphone
Micro Input Parameter/Conditions Min Typ Max Units
Maximum Input Level Range
Full scale single-ended voltage.
Signal applied to MICP with
MICN as reference.
1.03
V
PP
Input Impedance –
Mic(+) to Mic(-)
At 1 kHz. Impedance between
MICP and MICN.
1.5 k
Internal discrete high-pass -3dB
cutoff frequency
Differential MIC 70 Hz
Figure 24 : Microphone input
Component Value
C1, C2, C3 CONDENSER 22pF
L1, L2 Inductance 82nH