Hi, i'm  a new member.  Have been trying to connect a 4/4 switchbox to my direct tv.  i have a tuner/tivo all in one unit.  the switchbox i have has four inputs of 13v and 18v and has 4 outputs.  i connected the direct dich out to the input of the switchbox and then the output of 1 to my tuner/tivo unit, but got no picture??  what am i doing wrong??  also which of the two input connections should i use, the 13v or the 18 v???  thanks,  manny