LEMO 5-pin

1. +12 VDC to  +ve terminal battery

2. Data terminal ready

3. 0 V (common) . Also to -ve terminal battery

4. Transmit data Tx

5. Received data Rx

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RS232 - DB9

1. No use

2. Receive data Rx

3. Transmit data Tx

4. Data terminal ready

5. 0 V (common)

6. short to pin 7,8

7. short to pin 6,8

8. short to  pin 6,7

9. no use