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 obtained a master's degree in electrical engineering from the Royal Institute of Technology (KTH) in 1933. From 1935 to 1950, he worked for L. M. Ericsson and later received his doctoral degree in electrical engineering from KTH in 1950.