Complex sentence: In the early 1950s, he served as announcer for many of RCA's and NBC's closed-circuit color television demonstrations, but eventually became one of the top game-show announcers for the network.
Split into simpler sentences: In the early 1950s, he served as announcer for many of RCA's and NBC's closed-circuit color television demonstrations. He eventually became one of the top game-show announcers for the network.