From Buck Wiki, the ultimate Buck Rogers reference
Dr. Elias Huer retrieves the microtransmitter removed from Ranger 3, which had been placed atop a copy of a plastic case that enclosed a copy of the Holy Bible (BR25Film, "Awakening").

A microtransmitter is a recording and transmitting device.

Kane has Draconia's engineers plant such a device aboard Ranger 3 on the belief that William "Buck" Rogers is a Federal Directorate spy, and that he'll be permitted to land on Earth. In doing so, the microtransmitter gave the proper information on the planetary defense shield's pathways used by the Earth Defense Directorate. The device is later discovered, leading to Rogers' being charged for high treason and espionage for the enemy and sentenced for termination