The COM port is integrated in the 15 pin micro DSub socket on the right hand side of the instrument and allows for serial communication access to peripherial devices.
Technical information

The following pins are in use:

4: RTS
5: TXD
12: DSR
13: RD
14: GND

Inteface settings: 8 data bit, 1 stop bit and no parity.

The COM port is also called RS232 or V24 depending on your location.