Network and Bell TV. However, this is limited by the interval of the stream of keys or also called CW (Control Words). Usually, the interval for the renewal of the CWs is ±10 seconds, but other systems (i.e. NDS3) have CW intervals of 5 seconds or less. Each channel usually has a different set of CWs for decryption and thus each box currently watching a specific channel must periodically request the current CWs from the server/smart-card for that specific channel. So arguably, the sharing of the card might not be unlimited. There are some restrictions to this like the frequency of CW changes and also the latency of the network. If the CWs do not arrive in time, there could be a freeze or crackle in the picture. There are of course other more costly possibilities like having several legitimately subscribed cards each handling a few channels and a CW caching server. The dependence on an external server also compromises privacy for individual viewers, as well as rendering the system incompatible with many receiver models which lack the ability to connect to an outside network and/or lack the ability to set or modify the various keys or identifiers used in communication between the card and receiver. Common features Installation menu This is the main control panel that allows the user to configure the receiver to interact with LNBs, switches, motors, and other equipment. The user selects the LNB type, local oscillator frequency, appropriate DiSEqC switch port, and motor configuration. If all the settings are correct for the appropriate equipment, a signal bar showing strength and quality will appear. At that point, the receiver can be used to scan the satellite to detect channels. Blind scan There are 63 satellites in orbit over the Americas, 57 over Europe and a further 64 over Asia, a significant number of which will be receivable from any one location. Each of these has a different number of active transponders. Each transponder operates at a different frequency and symbol rate. Many FTA receivers are designed to detect any active transponders and any channels on those transponders. Because they are designed to do this without needing to be pre-programmed with the transponder information for each satellite, this process is referred to as a "blind" scan—as opposed to a satellite scan, which scans according to pre-set transponder values. Channel edit/sort Once a scan is complete, the channels