A Switch 3×4 Nanosat NS34ST is used by Sky, and possibly also for other carriers, in installations with 3 or more points, or with 2 points in at least one of them is HDTV Plus, that uses two cables (two tuners).
In these cases, a double LNBf, connecting the two outputs of the LNBf on the two satellite inputs Switch 3×4 (SAT IN 13V and SAT IN 18V). The outputs RX1, Rx2, RX3, Rx4 are connected to each point decoders.
It is also possible to mix the signal of VHF/UHF TV open so that each point can use a single cable to TV via satellite and terrestrial broadcast TV, useful in situations where you can't pass a second cable. This is possible because the LNBf converts the frequencies it receives from the satellite (microwave in the range of 10 GHz the 13 GHz, Ku band) for frequencies in the range of 950 a 2150 MHz, that are driven by coaxial cable with less attenuation and are understood by the decoder. Thus, the frequencies of 54 MHz a 806 MHz, used for VHF and UHF channels, are idle on the cable and can be used for this purpose.
If we need to separate the signal from the satellite and broadcast TV, as is necessary in older decoders you need TV module separate, or for anyone who wants to connect the VHF/UHF antenna directly to the TV, You can use a key Diplexer, that makes precisely the function of separating the satellite signal of VHF/UHF signal.
On the other hand, newer decoders, you already have the open TV embedded module can take advantage of the fact that open TV signal already being in the same cable.
A Switch 3×4 discharge power supply, It was used in older solutions, because it is fed by the decoders.
In facilities that need more than four cables (for example: four points, being a HDTV Plus), You can cascatear two Comutadoras 3 keys×4, connecting the two entrances of the second in two of the outputs of the first. The VHF/UHF signal needs to be inserted into each of the Comutadoras 3 keys×4, as shown in this schema released by Sky.