Jacobæus graduated from the Royal Institute of Technology (KTH) in 1933 with a master's degree in electrical engineering. In 1935 he went to work for L. M. Ericsson, where he would spend his entire professional career. In 1950 he received his doctorate in electrical engineering, also from KTH.
Jacobæus graduated with a master's degree in electrical engineering from the Royal Institute of Technology (KTH) in 1933 and began working for L. M. Ericsson. In 1950, he completed his doctoral studies in electrical engineering at KTH.