system headends, or other commercial users. While it is generally thought to be legal for home viewers to view such transmissions as long as they are not encrypted, this means that there are several unique challenges to viewing FTA signals, challenges not present in other areas of the world. Among these are: No schedule information is provided with most of the signals; therefore, satellite receivers cannot show a proper electronic program guide (EPG). Because many of these broadcasts are essentially point-to-point transmissions, the originators often do not follow any international standards when setting various identification fields in the data stream. This causes issues with receivers and software designed for use in other parts of the world, as they may assume that if a channel contains the same ID information as another channel, those are duplicate channels. This may be a valid assumption in other parts of the world, but is almost never valid for North American FTA signals. When such an assumption is made, during a "blind scan" the receiver or software will often fail to correctly insert one or more channels into its database, or it may overwrite previously scanned valid channels (including other channels on the same satellite) with invalid information picked up from another, more recently scanned channel. If the end user does not understand what is happening, they may assume that the receiver cannot receive certain channels or that it is defective, yet if the correct data for those channels can be manually entered, those channels may become receivable. This problem can be mitigated if receivers can be set to ignore channels that appear to be duplicates during a "blind scan", except when such channels are on exactly the same satellite and same transponder frequency (as might occur if the user rescans a previously scanned satellite). Channels tend to come and go, or change transmission formats, often without any prior notice other than to their intended recipients. This means that a working channel could suddenly disappear without warning, and may need to be rescanned to become receivable again, or it may be gone permanently. Channels that are currently FTA can become scrambled (encrypted) with no advance warning. A few channels tend to go back and forth between being "in the clear" (unscrambled) to scrambled at various times, but in most cases, once a channel is scrambled it stays scrambled. Historically, it has appeared that broadcasters are