What are dSCR multiswitch used for ?

They are generaly used with Terra Electronics TDX / TTX  range of Transmodulators to allow selection of programming from all satellite transponders.

They are used in a  SINGLE  coax cable system to distribute satellite & terrestrial programmes to viewers with UNICABLE set top box or SKY Q boxes.  The satellite signal source can be from a quatro or wideband LNB.

Can they be used in a legacy multiswitch situation ?

 Yes they can be inserted in cascade without affecting viewers services whou are using legacy SKY or free- to- air set topboxes. Viewers  can have a choice of either  signal source.

What is the limit of viewer outlets available from TERRA Electronic dSCR multiswitch. 

SRM522 32 userbands per pair. SRM581 8×4 pair