The Zectronic Beam Controller was a device used to contain and control zectronic energy beams.
Such a device was installed aboard a spaceship operated by the Daleks, who had been granted the secrets of zectronic energy by the Master. Believing the Master to have betrayed them as a result of the captive Ninth Doctor's attempt to communicate with him, the Daleks accidentally hit the Zectronic Beam Controller with a stray shot from a gunstick. To prevent the Zectronic Beam Controller from simultaneously exploding and imploding, the newly regenerated Tenth Doctor attempted to fix it, however, as he "forgot to unplug first", sustained injuries which forced him to regenerate into the Eleventh Doctor, who in turn regenerated into the Twelfth Doctor. Though the Zectronic Beam Controller had been fixed by that point, an act which earnt the Doctor the gratitude of the Daleks, a stray discharge of pure zectronic energy hit the Doctor, resulting in his regeneration into the Thirteenth Doctor. (TV: The Curse of Fatal Death)