 Nevertheless, by splitting the network into two stages, considerable economy could be affected.To connect the allotted registers to the calling line, the MCU asked the interrogator-markers to identify all free paths from the subscriber to the central, "through" type, links and from the register to the links.This information was returned to the Route Choice Unit, which then identified those link circuits, which were available to both peripheral terminals, and selected the most suitable, according to predetermined rules chosen to make maximum use of the network.