Actually the AN/PSN-10 SLGR is an L1 only machine that doesn't use P-code at all as there's no provision for Fill. While there are two connectors for U-229 plugs on the side -- the first is power, and the second is DATA OUT available in either Trimpack or Transpack format. That's the reason they turned off Selective Availability ('SA') for the First Gulf War as while they had a number of P-code machines out there - they didn't have nearly enough - hence the need to purchase a few thousand of the no-code, largely civvy machines - and turn the SA off to keep both military machines and civvy machines at nominally the same accuracy.
The next generation of the military 'green' SLGR/Trimpack/Transpack family was the AN/ASN-169 SAGR (also called the Centurion) which were made both as new production and rebuilt older AN/PSN-10s returned by the Gov to Trimble for upgrade which came back with L1/L2 and P Code capability (though L1 only on the internal antenna.)
Uncle finds it a bit hard to keep straight too as even the no-code, no-fill, civvy-trimpack-in-a-green case SLGR gets Demil coded the same as the Centurion even though it contains no CCI at all.
