SimCom RS-232 Quick Start Manual page 5

Connection Details
Sr. No. Connection / Terminal
1 DC Jack (X8)
2 DB9 Female Conn (X4)
3 RJ11-4 Conn (X3)
4 TX (X1-1)
5 RX (X1-2)
6 ADC (X2-1)
7 RTC (X2-2)
8 DTX (X2-3)
9 RTX (X2-4)
10 GND (X2-5)
11 +5V (X2-6)
12 POUT (X3-1)
13 DTR (X3-2)
14 DCD (X3-3)
15 DBR (X3-4)
16 CTS (X3-5)
17 RTS (X3-6)
18 SCL (X4-1)
19 SDA (X4-2)
20 PWM1 (X4-3)
21 PWM2 (X4-4)
Details
DC Input
RS232 Connector
Audio Connector
Transmit Pin of SIM900
Receive Pin of SIM900
ADC Input Pin
Power Supply for RTC
Debug Tx
Debug Rx
Ground
+5VDC Out Pin
NC
Data Terminal Ready
Data Carrier Detect
NC
Clear to send
Request to Send
I2C Serial Bus Data
I2C Serial Bus Clk
PWM1 OUT
PWM2 OUT
Note
7-15 VDC Input
Input Voltage Range 0V to 2.8VDC
3V External Battery
for debugging and upgrading
firmware
Circuit Ground
+5DC 200mA Max