So, what is the main difference between RS 232 and RS 422 & 485? The RS 232 signals are represented by voltage levels with respect to ground.
There is a wire for each signal, together with the ground signal
(reference for voltage levels). This interface is useful for point-to-point communication at slow speeds. For example, port COM1 in a PC can be used for a mouse, port COM2 for a modem, etc. This is and example of point-to-point communication: one port, one device. Due to the way the signals are connected, a common ground is required. This implies limited cable length ? about 30 to 60 meters maximum. (Main problems are interference and resistance of the cable.) Shortly, RS 232 was designed for communication of local devices, and supports one transmitter and one receiver.

RS 422 & 485 uses a different principle: Each signal uses one twisted pair
(TP) line-two wires twisted around themselves. We’re talking ‘Balanced data transmission’, or ‘Differential voltage transmission’. Simply, let’s label one of the TP wires ‘A’ and the other one ‘B’. Then, the signal is inactive when the voltage at A is negative and the voltage at B is positive.
Otherwise, the signal is active, A is positive and B is negative. Of course, the difference between the wires A and B matters. For RS 422 & 485 the cable can be up to 1200 meters (4000 feet) long, and commonly available circuits work at 2.5 MB/s transfer rate.

What is the difference between RS 422 and RS 485? Electrical principle is the same : both use differential transmitters with alternating voltages 0 and 5V. However, RS is intended for point-to-point communications, like RS 232. RS 422 is intended uses two separate TP wires, data can be transferred in both directions simultaneously. RS 422 is often used to extend a RS 232 line, or in industrial environments.

RS 485 is used for multipoint communications: more devices may be connected to a single cable- similar to e.g ETHERNET networks, which use coaxial cable. Most RS 485 systems use Master/Slave architecture, where each slave unit has its unique address and responds only to packets addressed to this unit. These packets are generated by Master (e.g PC), which periodically polls all connected salve units.

If an interline-transfer-CCD-image sensor is read out, the generated charge carriers are transferred from the light sensitive part (photodiode) of a pixel to the shift register, which is next to the photodiodes and acts like a potential bucket. Because of the weak light sensitivity of these shift registers, they are shaded to prevent the additional generation of charge carriers. When the charge transfer to the shift registers is complete, they are shifted vertically row by row to the horizontal readout line, which is read out in a serial way. This vertical shift of row by row can be best compared with an endless conveyor belt process. With every shift step all registers are shifted by one register location including register rows that were already drained from the image.
If an intense light source is imaged to the CCD-image sensor, this can generate unwanted charge carriers in the shadowed shift registers (mainly due to scattering of light on the CCD ship) in every line or row, which is shifted below the spot. This results in unwanted additional light signals, called “smear”, which can be recognized as bright vertical bands above and below the bright image spot. This phenomenon is more often seen at very short exposure times (because the light signal has to be intense to achieve a good image with a sufficient signal-to-noise ration) and is a characteristic of the corresponding CCD-image sensor.