EIA-232 / V.28 (V.24), Male DB-25 Connector Pin CCITT Description 2 103 TxD 3 104 RxD 15 114 TxCLKi 17 115 RxCLKi 4 105 RTS 5 106 CTS Shell n/a CGND 20 108 DTR 6 107 DSR 8 109 DCD 24 113 TxCLKo 25 125 RI 7 n/a GND