RS - 232 is one of the communication interface on a computer, by the electronic industries association (ElectronicIndustriesAssociation, EIA) asynchronous transmission standards promulgated by the interface. Usually the RS-232 interface comes in the form of 9 pins (DB-9) or 25 pins (DB-25), and there are two groups of RS-232 interfaces on general personal computers, called COM1 and COM2.