After obtaining the blueprints for the Hyperbolic Time Chamber from Kami, He-El contacted Bulma and her father, Dr. Briefs. Both were very interested in the modifications He-El had proposed for the Hyperbolic Time Chamber, so He-El brought them to Kami's Lookout to begin surveying and modifying it.
Kami was very displeased that He-El had casually brought people up to Kami's Lookout, but he knew there was no way to stop him. Since He-El had only brought them up to modify the Hyperbolic Time Chamber and had done nothing else, Kami decided to stay out of sight and remained in his house, rarely coming out.
Thus, Goku, Piccolo, Krillin, Yamcha, and Puar were beaten and trained by Mr. Popo in the plaza of Kami's Lookout. He-El had deliberately told Mr. Popo to hit them harder.
Meanwhile, He-El studied the Hyperbolic Time Chamber with Bulma and Dr. Briefs and carried out its modifications.
This project took far longer than He-El had expected. It took more than half a year before He-El, Bulma, and Dr. Briefs finally completed the reconstruction of the Hyperbolic Time Chamber.
Naturally, it differed somewhat from the one Kami had built.
Besides removing the two-day limit and changing it to no time limit, He-El, Bulma, and Dr. Briefs also added gravity control to the Hyperbolic Time Chamber. It could now be adjusted from a minimum of ten times gravity to a maximum of one hundred and fifty times gravity.
They also adjusted the temporal signal frequency inside, allowing communication with people outside. This real-time time-converted signal communication system was Bulma's proud masterpiece.
Even with one day passing outside and one year passing inside the Hyperbolic Time Chamber, as long as someone outside contacted a person within it, they could communicate without obstruction through Bulma's real-time time-converted signal communication system.