According to the FBI:
The FBI Public Access Line, or PAL, will take calls, faxes, e-mails, and more out of the Bureau’s 56 field offices and centralize them. Bureau employees with specific training to gather as much information as possible staff the line around the clock.
The below were requested in May of 2018. They were finally released in late September of 2020.
The FBI’s Public Access Line (PAL) Manuals and Procedures, Released 2020 [741 Pages, 340MB]