RS232 serial interface basics

Now more commonly used RS232 serial 9pin d-shaped serial [DB9] and 25pin d-shaped serial [DB25], the maximum communication distance of up to [15m]. The short distance between two devices close, 232 of them with 232 cable directly connected to the serial port if distant, via modem (MODEM) connected.
RS232 interface
Negative logicthe output is represented by +5V~+15V [0],-5V~-15V said the logic [logic 1].
Single drivethrough the data sender [TD] output driver circuit, and signal GND as reference points.
Receivingby the data receiver [RD] enter the receiving level and to signal GND as the reference point.
RS232 wire
To achieve [point-to-point bi-directional communication] requires 3 communication cable, host the data sender [TD] with data from the receiver [RD] connected to host the data receiver [RD] with data from the transmitter [TD] connect two signal ground [GND] is directly connected to.
RS232 notice
RS232 serial ports cannot be directly connected to the RS485 serial portbecause they have the same electrical standards; serial converters available on the market, must pass through the converter to connect. Also, do not plug, and plug when there is at least one end is powered down, or easily damaged serial port.