Simply, what is a RS-422 line? Additionally, what does it do/is it used for?
In: Technology
It’s a serial data transmission line. Cheap, simple, slow, doesn’t really mind being strung all over an industrial plant for half a kilometer with not super well shielded wiring.
Rs-422 uses a pair of Differential signals for each line, hence is less susceptible to induced noise from the environment.
[deleted]
Rs422 is an industrial version of a serial communication line. Instead of a single TD and RD wires, both transmit and receive lines are balanced pairs (two wires). Similar to ethernet wire pairs. Because they are balanced, they have higher noise immunity, which allows longer transmitting distances and better reliability in electrically noisy environments with lots of motors.
RS stands for “Recommended Standard” and the number indicates which standard: RS-232, RS-422, RS-485, etc…
It doesn’t specify what it is used for, only the electrical specifications.
RS-422 is a
* single master
* serial transmission line, using
* differential signaling (-6V/6V), in a
* point-to-point, but multi-drop, bus topology
Based on these specifications, it might be (un)suitable for certain use cases.
In the past, RS-422 was commonly used to increase the transmission distance of RS-232 signals, by using a signal converter.
Several answers explaining what it is. What is it used for? In my experience: Control and automation of factory equipment, scientific instruments, and other machines. Also, diagnosis and repair of more complex electronic equipment when other means of control have failed.
It’s very old and uncomplicated, which can be an advantage where “cheap” and “easy to implement” is more important than other features.
Have you ever heard of that tin-can phone? Two people, each with a tin can, and a wire running between them. If it’s stretched tight, one person can speak into the can and the other person, with their ear in the tin can, is able to hear them. Pretty neat. Put it between houses across the street and you can sorta do a phone line.
But you can’t really talk and listen at the same time, since you have to switch between speaking into the tin can, and putting the tin can up to your ear.
What if you have *two* tin cans? One for your mouth and the other for your ear? Then each person has two tin cans, and you would run a wire between each pair. Now you can talk and listen at the same time! That’s RS-232. One person’s *mouth* tin-can (transmit) wires up to the other person’s *ear* tin-can (receive) and vice versa. There’s actually a third wire, called *ground*, that’s kind of needed for your special tin cans to know that the vibrations on the wire is actually someone talking and not, say, the wind outside rattling your wire.
That might work if your houses are across the street from one another. But what if you want to talk to your friend that’s a few houses further down? The loudness (signal strength) gets weaker the further you are from one person to the other. How could we make that better? Well, that ground wire from RS-232, we could make it a dedicated wire for the transmit line. And we could make another for the receive line. So now your *transmit* tin-can has two wires to the other person’s receive line, and vice versa. And your special tin cans, instead of using the original *ground* to figure out if the vibrations is actually a voice, now uses the pair of wires between the cans. That’s RS-422
Latest Answers