Climbing indoors at my regular wall with a frequent climbing partner, who was approximately five or six stone heavier than me. Device used was an ATC (roughly 15 years old and quite worn). Climber slipped around 9 metres, at the point that I was paying out slack with the hand on the dead rope above the device - and also distracted by a friend entering the climbing wall. I was pulled up to the first quickdraw, and the climber decked. The only injuries were moderate rope burn to both my hands. The climber was uninjured.