Introduced with software version 1.02.13
Home, Settings, Channel Settings, Automatic Channel Search - Note the new on screen message.
The Smart option will retune keeping your recording schedule and favourites intact for those mux/channels/LCN's that remain unchanged, ie identical to previously stored . If the Mux or LCN is changed then any associated recording schedule and/or favourites will be removed.
Note: You may have to carry this out twice if an LCN is changed but remains in the EPG with different contents eg original channel moved to a new LCN and current LCN occupied by another channel.
The Default option is as before, schedules and favourites will be deleted and have to be re entered.