System Capacity (Maximum) :
Extentions (Max), 3 shelf. ( DPT + SLT ) = 448 port CO lines / Trunk lines (Max) 3 shelf  = 192 Port Total (Max) 3 shelf, CO lines + Extention lines = 512 port

Optional :
Digital Trunk : ISDN (T1 & E1), BRI ISDN, PRI ISDN, Tie Line ( E & M ), Direct Inward Dialing Trunk DISA ( Direct Inward System Access ), Remote Maintenance, Metering by Polarity Reverse Detection for Billing System