This is a DB9 male connector with a private pinout describe below.
Pin Signal Description Direction
1 - unswitched (+5v at 10 uA) output
2 TxD transmit data output
3 RxD receive data input
4 RTS ready to send output
5 CTS clear to send input
6 - reserved for future use -
7 GND Ground
8 DCD data carrier detect input
9 DTR switched (+5v at 1mA) output
Note : DTR is high when the machine is awake. The machine is always awake when the screen is active, but even if asleep the machine will wake every minute or so to carry out various housekeeping tasks, such as checking for alarms, and at these time DTR will go high. Pin 1 will show a signal if there is power available to the machine.