In discussing the similarities and differences between the sonic pen and sonic screwdriver, the Tenth Doctor implied both were of similar manufacture despite his screwdriver having apparently come from his TARDIS. The sonic pen was able to open deadlock seals, but only ones it was coded to, while the Doctor's device remained ineffective against that precaution. When the Doctor put the ends of the functioning sonic pen and the sonic screwdriver near each other, they generated a feedback effect which stunned everyone in the vicinity. The pen was invaluable in stopping the Adipose' sinister plot as it allowed the Doctor to access the otherwise triple-deadlocked inducer. After the death of Cofelia, the Doctor threw the sonic pen into a bin. (TV: Partners in Crime)