Command Interface Logic
command interface logic, also referred to as the ground command
interface logic controller, controls many of the functions of the
S-band PM, S-band FM, Ku-band, payload communication and CCTV systems.
Commands are sent to the orbiter from the ground through S-band
system uplink or Ku-band system forward link. All commands, whether
sent on S-band or Ku-band, are routed to the onboard GPC through
the NSP and associated MDM. The GCIL takes commands for these systems
from the GPCs for ground commands or from the appropriate panel
for flight crew commands. The command source is selected at a control
panel pnl/cmd switch for each system. If the switch for that system
is on pnl, the flight system is in control. If the switch for that
system is on cmd, the ground has control.