DB-9F connector for PC host connection

Supports 3V to 5V logic levels

4-Pin connector for logic connection

Operates on 3VDC to 5VDC

Pinout for 4-Pin Logic Connector
Pin-1, Brown: RxD (from PC's TxD)
Pin-2, Yellow: TxD (to PC's RxD)
Pin-3, Black: Ground
Pin-4, Red: 3V or 5V (depending on logic requirements)