The Digitize Form Four is a power regulator that provides power, supervision and control for 100MA telegraph boxes. The Form Four prevents excessive generation of heat which could damage circuitry and reduce the life of the equipment. The Card Cage provides the housing for one common card, and up to 10 Box or Alarm cards in any combination. The Form Four Box Card supplies supervisory and control logic for repeating alarms to bell or recording circuits. It also automatically provides ground return capability for the reception of alarms from “Three Fold” type fire alarm boxes in the in the event of an open circuit.