Voltage blocks are used primarily with preamplifiers when a signal splitter is installed in between the outdoor mast mounted preamplifier at the antenna and the indoor preamplifier power inserter. They are installed on all output ports of the splitter except for one. The output line that leads from the splitter to the power inserter. The voltage block screws directly on to the splitter. Also the antenna input on the splitter does not require a voltage block. This allows the power from the indoor power inserter to travel through the signal splitter directly to the preamplifier at the antenna and not to the remaining TV outlets.