was substantially better than its competition, Hollerith and Powers, through the mechanism of punched card pre-selection. The machine proved a success and received very good reviews and publicity The key factors for success were the technical quality of the machine, the ease of use, the new pre-selection technology, the cost savings and the opportunity for users to avoid IBM's monopoly and purchase their own equipment instead of renting it. Other patents Bull continued working on improvements for the machine and also in developing new machines such as a sorting machine and a new tabulating machine. Some of the notable improvements were: the change of switches that controlled the entry of punched cards and the expansion device in larger scale. The reading device was the most critical part of the machine. Built with electrical conductors or springs, punched cards were introduced, the springs passed through the holes producing contact. The springs only passed through the holes of the punched cards, causing the information to be recorded. He obtained the ideas for this machine by stealing the notes of Henrik Hartzner, his Danish partner. One of the main problems of this method was the low durability of the material of the cards, which meant that the method did not always work the right way. Another major problem was the dust that entered the holes of the contacts. Finally, one of the biggest problems Bull and Knutsen had to face was that because of the contacts, sparks were created causing the machine to crash frequently. All these details were being constantly improved. Production of Bull machines was rather slow. In 1921 there was a production of 2 machines, 2 in 1922, 2 in 1923, 4 to 1924 and 6 in 1925, distributed among companies in Norway, Denmark (Hafnia as a notable client), Finland and Switzerland. There were constant problems with the machines; Knut Andreas Knutsen was continuously traveling to these countries for repair and modifications at client sites. Illness and death In the summer of 1924 Bull was diagnosed with cancer, a disease that ended his life on 7 June 1925 when Bull was only 42 years old. Despite the diagnosis in the summer of 1924, Bull continued to work until his condition worsened in the fall of that year. In the last few days he shared his latest ideas with Knutsen. Bull's patent rights were acquired by Oka, where Knutsen, loyal to