RS232 describes the common voltage levels, electrical standards, operation mode and number of bits to be transferred from DTE to DCE. This standard is used for transmission of information exchange over the telephone lines. Electrical Standards There are other pins for control, but they are not necessarily used. Their main function is for buffer retention control.

Initial speed was 12 Mbps, increased to 480 Mbps with USB2 and up to 5 Gbps "Superspeed" mode with USB3. The protocol in RS-232 is quite simple. It is assumed that both sides are initially silent (each TX is low), and then when a side wants to transmit a byte it does one or more high pulses (the "start bits"), sends each bit of the byte transmitted sequentially and then finishes with some more pulses ("stop bits"). Optionally, there may be a parity bit. It is assumed that both sides previously have the same configuration for start and stop bits and the timing for sending each bit (the baud rate). The flow control of data transmission and reception is done using hardware handshaking. It uses control signals DTR, DSR, RTS and CTS signals. Typically, when establishing communication between a computer and modem RTS and CTS signals are used.Control and configuration is all done with software using data signals which are an utterly inseparable part of the interface. Observing the data stream with an oscilloscope will not reveal the actual data component of the system. When ‘XOFF’ character is enabled, the communication is closed until ‘XON’ character is received by the transmitter. In some cases, the receiver buffer may overload which causes the receiver to send ‘XOFF’ automatically to the transmitter. How Handshaking Works? There are no cable length limits defined directly by the RS-232 standard, so the main determining factor is the maximum capacitance tolerated by a compliant drive circuit. As a general rule, the critical length will be 15 m (or about 300 m provided that only low-capacitance cables were used). Frankly speaking, For longer distances, the RS-232 standard isn’t the best option for high-speed long-distance data transfer. was (and to some extent still is) a very useful powerful flexible way of connecting computing device to peripherals.

According to the RS-232 standard, all data is bi-polar. For most equipment, an ON or 0-state (SPACE) condition is indicated by voltage from +3 V to +12 V and an OFF or 1-state (MARK) condition is indicated by voltage from -3 V to -12 V. However, some devices don’t recognize any negative levels and 0 V is enough for the OFF state. And sometimes smaller voltages can be enough to achieve the ON state. Thereby it’s possible to significantly reduce the overall range for RS-232 transmission/receiving. The electrical characteristics of RS232 defines the specifications related to voltage levels, line impedance and rate of change of signal levels. Voltage Levels

RS-422 was used with a smaller 8-pin mini-DIN connector on early Apple Macintosh computers to connect to AppleTalk networks and various peripherals. RS-422 is also found on professional video broadcasting equipment. That’s all! Now, Windows will search for the driver and other system updates. If found, Windows will automatically install the available ones. Once the updates are successfully installed, reboot your computer to save new drivers.