DNA coder

A DNA coder was a metal band which transformed and regulated its wearer's DNA, allowing them to disguise themselves.

Trenix used a DNA coder, which Ann Kelso mistook for a health band, in order to take human form. The Fourth Doctor shot at Trenix with a Sinestran killrod set to stun in order to interfere with his coder, forcing him to return to his alien form and frighten away Hugo Blake and his men. (AUDIO: The Sinestran Kill)