Maestro 100 2G Series, Quick Start Manual & User Manual, Page: 20 / 31

5.1.3 15-Pin D-Sub Female connector (RS232/Audio)
This connector provides serial link and audio link to the modem.
Pin Number Name EIA designation Type Note
1 DCD Data Carrier Detect Output
2
TX Transmit Data Input
3
BOOT Input
4 MICR Input With 2VDC bias output
5
MICROPHONE - Input With 2VDC bias output
6 RX Receive Data Output
7
DSR Data Set Ready Output
8
DTR Data Terminal Ready Input
9 GND Ground Ground
10
S Output
11
CTS Clear To Send Output
12 RTS Request To Send Input
13
RI Ring Indicator Output
14 RESET Input Pull low for 100ms to reset,
module requires 5-7s to reboot
15 SPEAKER - Output
Specification of microphone and speaker to be connected:
Parameters Min Typical Max
Microphone current @2V/2K Ohm 0.5mA
Microphone input level 100mVpp
Speaker output current 150 Ohm/1nF 16mA
Speaker impedance 32 Ω 50 Ω
Please refer to the document "Application note - Power supply & Audio" for more information about audio connection.
CAUTION
If the CTS and the DTR signals are shorted together, the modem will enter a factory download mode. In this mode,
the modem does not behave in a normal manner and can not connect to the cellular network.
It is recommended that CTS and DTR pins should never be short-circuited. If the application requires to use "flow-
control spoofing" cables, make sure that they do not connect CTS to DTR.
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