system controller 34 pivots down 34 device staging station 400b it valves port s 0 off and ports s 1 s 2 s 3 and s 4 on the lead device sliding from tube 1 upon pivot down of device staging station 400b is braked and arrested to a stop over one of ports s 1 s 2 s 3 or s 4 by vacuum applied at ports s 1 s 2 s 3 and s 4 system controller 500 then valves vacuum at port s 0 on and next valves vacuum at ports s 1 s 4 off this arrests the device over s 0 and all trailing devices in slideway and permits all devices forward of port s 0 to slide down slideway 475 to any next unoccupied position thus filling the positions over ports s 1 s 2 s 3 and s 4 if there are a sufficient number of devices to do so system controller 500 then valves ports s 1 s 4 vacuum on and inspects to confirm vacuum at ports s 1 s 4 if vacuum is not confirmed at all of the ports s 1 s 4 simplying one or more of the ports has no device in place over it for pickup system controller 500 inspects port s 0 for vacuum if vacuum exists at port s 0 implying a device over port s 0 and perhaps a train of devices held behind it the system controller valves vacuum to port s 0 off permitting the device over port s and next trailing devices to slide down slideway 475 for arrest by vacuum still on at ports s 1 s.