RS-232C is short for Recommended Standard 232 C.

The letter C refers to correction, meaning that the standard is a corrected version. “232” is the identification number.

RS-232C is a strict standard that specifies the connection cable, machinery, electrical characteristics, signal function, and transmission process. 

An RS-232C port is widely used as transmitting computer signal to projector.


TxD and RxD: Logic 1(MARK) =-3V ~ -15V 

Logic 0(SPACE)=+3 ~ +15V 

Control lines such as RTS, CTS, DSR, DTR and DCD: 

Signal valid (ON, ON, positive voltage) = +3V ~ +15V 

Signal invalid (OFF, OFF state, negative voltage) = -3V ~ -15V 

In order to realize serial communication, PC usually has two serial interfaces in line with RS-232C standard and uses the serial controller composed of universal asynchronous receiver/transmitter control chip UART to process the sending and receiving work of serial data. The serial interfaces on PC usually use DB-25 or DB-9 connectors of 25 or 9 cores.  It is mainly used to connect MODEM devices for work. Therefore, the RS-232C standard specifies many special MODEM interface leads.