When the slab is pulled out of the freezing chamber, it already has a series of diagnostic panels along its edge. One of the panels (the one nearest to Han's head) has the ability to report Han's vitals.
Considering that the carbonite freezing process at Cloud City was purely an industrial process with no medical purpose, it is somewhat strange for the final product to have such a panel.
It seems that the panel for the vitals was sourced from Cloud City itself, as it is Lando — not one of Vader's entourage — who reads it and reports that Han has survived.
If the freezing chamber was not specifically altered for the occasion, why would it have such a diagnostic panel?
If it was altered for the occasion, how far in advance was the chamber altered, and was it done by Lando's staff or Vader's people?
How is the panel even powered? Does the freezing process install a battery, too?