Complex sentence: The earlier research and development work of TRE and RRDE on radar, solid state physics, electronics, and computer hardware and software was continued in the merged establishment, and the overall scope was extended to include cryogenics and other topics.
Split into simpler sentences: The earlier research and development work of TRE and RRDE on radar was expanded into solid state physics, electronics, and computer hardware and software. The RRE's overall scope was extended to include cryogenics and other topics.