The Sonic pen was a sleek black device used by Matron Cofelia that functioned in a similar fashion to the Doctor's sonic screwdriver.
In discussing the similarities and differences between the sonic pen and sonic screwdriver the Doctor implied both were of similar manufacture. The sonic pen was able to open deadlock seals in the Adipose Industries headquarters, while the Doctor's device remained ineffective against that precaution (Her pen may have had unlock codes for her building, so it may not have unlocked a deadlock seal). When the Doctor put the ends of the functioning sonic pen and the sonic screwdriver, it generated a feedback effect which stunned everyone in the vicinity. After the death of Cofelia, the Doctor later threw the sonic pen into a bin. (DW: Partners in Crime)
Behind the Scenes
- A toy replica of the Sonic Pen was released by Character Options in a two-pack with the Doctor's Sonic Screwdriver. Both now featured a non-Ultra violet-blue LED and identical sound effects. A single button built into the clip would activate the light and sound effects, and twisting the casing of the pen would extend the ink tip. Compared with the prop that appeared on-screen, the toy features an added section around the emitter, probably to house the LED and switch.