A blast hole drill comprising a mast including two parallel mast cords, a carriage, and a rotary head mounted on the carriage and adapted to engage a drill pipe. The desired level of comfort and easy of use to the wearer is achieved by constructing the headband at least partially from stretchable material and incorporating a sweat absorbing foam inner layer. The cutter brackets are mounted on the base. Possible events that can be generated in the identified monitorable points are then identified to define the monitorable events. An energy calculator in the receiving device calculates the energy of each decided symbol.