What’s the difference between FXS and FXO?

What’s the difference between FXS and FXO?

It’s easy to get lost in the confusion of FXS and FXO, especially if you’re a complete novice in matters of VoIP (Voice over Internet Protocol). These terms are often used in the telecom world, and understanding their difference is the first step in choosing the right VoIP system that best suits your needs.