In a statement issued at 7:00(BST) this morning, Sweden's Ericsson makes it clear it is most interested in Marconi's transmission offerings, saying the UK company's optical technologies will complement its own microwave radio position.
Together, the assets being bought represent three-quarters of Marconi's turnover.
The transaction value is SEK16.8bn (£1.2bn).
The deal does not cover Marconi's headquarters and certain businesses in Germany and the UK, nor does it include the company's pension plan.
Marconi has struggled to articulate an independent future for itself since losing out on contracts for a £10bn network upgrade by BT, traditionally its largest customer.
There had been speculation Marconi might be bought by a Chinese vendor, possibly Huawei, aping the deal whereby some assets of car-maker Rover were eventually sold.