A digital cliff is a point at which a digital signal is no longer receivable. A curious feature of digital signals is that such signals either come through, or they don't. There is no gray area in which a signal can still be received, albeit a fuzzy one, as there is with analog signals. The digital cliff effect, as it is known, has a profound impact on a wide variety of devices which rely on digital signals, such as televisions, radios, and cellular phones.
The “cliff” in “digital cliff” is a reference to the way signal strength appears on a graph. As someone is close to the signal, the graph remains high, but at a certain point, the line drops precipitously, resembling the profile of a cliff. Analog signals, on the other hand, present gentle slopes as the signal quality slowly declines.
With an analog signal, as a user moves away from the signal with a device which picks up the signal, as the signal weakens, the output may be fuzzy, but still coherent. Eventually, the distance will be so great that the signal cannot come through at all. Digital signals, on the other hand, simply cut out at a certain distance, with the signal remaining perfect up to that point.
In many regions of the world, people use a mixture of digital and analog signals. As more and more industries switch to digital-only, some people are concerned that the digital cliff could become a real issue. Cell phone users, for example, would lose service in many areas where they had service before once analog signals are switched off. People can use antenna extensions and other tools to get a stronger digital signal, but these solutions are not always effective, depending on where the user is.
To counter the digital cliff effect, more digital signal relays are needed, to ensure blanket coverage of target areas. Especially in regions where people are accustomed to getting a signal on devices which can pick up weak analog signals, consumers could be extremely upset by the effect that the digital cliff would have on their televisions, radios, and cell phones. In response to a growing push for all-digital signals in places like the United States, some savvy companies have started offering antenna extenders to their customers so that their services will not be interrupted by the switch.