Abstract: A field-of-operation illuminating device has at least one discharge lamp concentrically surrounded by several halide incandescent lamps at its bottom, which faces the field of operation. The discharge lamp is accommodated in a stationary reflector and illuminates the recesses of the field. The incandescent lamps are mounted in reflectors that can be adjusted so that their beams will overlap in the field. In the event of power outage or failure of the mains, power is supplied to the lamps from a battery-supported substitute source. The incandescent lamps, due to their thermal inertia, continue to burn almost uninterruptedly, whereas the discharge lamp remains off long enough to cool-down before being restarted. The advantages are less heat during normal operation and immediate availability of the incandescent lamps in an emergency.