This is really determined by the service provider and user, there is not any specific answer.
Most providers use either and 8 pin modular jack wired to RJ-48X or a DB-9 connector. See link to RJ wiring scheme http://www.levitonvoicedata.com/learning/wiring.aspx
At the customer patch panel I would normally suggest that they use RJ-48X panels so that the loop-back shorting bars are there when no patch cord is inserted. Again, the actual needs of the user may be different.
Joseph Golan, RCDD