Pin numbers are read left-to-right with the connector tab facing down.
568A vs. 568B
When installing additional wiring into an existing facility, it is usually best to determine which wiring standard is currently in use and conform to that standard.
The most prevalent standards are TIA/EIA 568A and TIA/EIA 568B.
When installing telephone wiring into a new facility, EIA/TIA 568A is the standard to utilize.
