Some time in 1979, Zircon International bought the rights to the Channel F and released a re-designed console under the name Channel F System II. The II re-design was done by Nick Talesfore, the same industrial designer who created the original console.
The major changes from the Channel F were in the physical design of the console, with the System II having a simpler and more modern looking appearance. The fragile controllers were now removable, allowing them to be unplugged from the System II for storage or replacement (the original Channel F controllers were hardwired directly into the base unit). In addition, the System II eliminated the covered controller storage compartment, replacing it with two open compartments at the back of the console which the controllers fit into for storage.
One notable functional change was introduced in the System II. The sound effects were now mixed into the TV signal so that they would come from the TV. The original Channel F provided sound effects through a speaker built into the console.
Only six new games were released before the death of the System II. Several of these had been developed at Fairchild before they sold off the system.
Source: Wikipedia, "Fairchild Channel F", available under the CC-BY-SA License.