If in case you are not familiar with what these two are, these are known to be tuners. NTSC stands for National Television System Committee while ATSC stands for Advanced Television Systems Committee.
These two would need different things in order to work properly. NTSC has been around since the year 1941 and is considered to be the current standard while ATSC is relatively new and this started out in the year 1995.
If you would check out the HDTV sets that are available right now, they are already equipped with ATSC tuners as compared to the NTSC tuners. The ATSC will be very helpful in trying to get digital channels to be watched on the television.