RJ21

RJ21 is like a big telephone wire that connects lots of small phone wires together. It helps people talk to each other on multiple phones at the same time. Instead of having lots of individual phone wires that can get tangled up and confusing, RJ21 organizes them all into one bundle, like putting all your toys in a toy box. That way, people can easily call each other without getting mixed up or losing track. It's like a phone party line with lots of people talking at once, but everyone can still understand each other because RJ21 helps the phones work together.