Sec. 68.506  Configurations used to connect multi-line communications 
          systems such as Private Branch Exchange (PBX) and key 
          telephone systems.

    Any of the jack configurations specified in Sec. 68.502, used 
singly, in multiple combinations, or combined in common mechanical 
arrays, may be used as the interface between multi-line equipment such 
as PBX and key telephone systems, and the telephone network. The 
telephone company and installation supervisor may mutually agree to use 
electrical connections alternative to those specified in Sec. 68.502.

[43 1997 FR 16501 , Apr. 19, 1978]