Originally it was (what is now basic) electronic devices (like door bells) and intercoms.
Owned by Eric Moll and family, they migrated to radio around the time of CB radio.
Multisource were the General Electric agents in South Africa for CB and Two-Way Radio back then.
The company was called Executive Communications, and at one stage, were the largest radio paging operator in the country, with branches in Jhb, Vaal, Pretoria, Cape Town, PE, and Durban (called Quickvoice).
Execom was also the first commercial company in South Africa to have a full Class C block of IP addresses (obtained from the US Government, before Afrinic etc) and connected via what was then Uninet, which was subsequently termed "the internet".
Along with the paging operation, they were radio telephone interconnect operators, with localised systems in each of the main centers, as well as a radio network which ran from Durban to Johannesburg, labeled Highway 66, which then became Highway Communications.
With the advent of Cellular technologies, these radio and paging systems became (for the most part) redundant. Over the years, they have progressed with technology and are now poised to compete with the larger networks.
Yes, spectrum played a large part in the acquisition, but not the only part.
One will have to just wait a little while before you see where the company is heading.