Jimmy Olsen's signal watch

Jimmy Olsen's signal watch is a fictional technological device featured in comic books published by DC Comics. It is associated with the Superman line of titles and was introduced during DC's Silver Age, Earth-One era of continuity.

The signal watch was created by Superman and given to his best pal, Jimmy Olsen. On the surface it appears as nothing more than an ordinary wristwatch, but it has a switch that when pressed, emits a sub-sonic signal that only with someone with enhanced hearing, such as a Kryptonian, can perceive. Superman can hone in on the signal, and by extension track Jimmy Olsen down no matter where he is located.

Superman gave Jimmy the signal watch for the purpose of activating it in times of need, whenever Jimmy was in life-threatening danger, or if he was in the vicinity of a situation that required Superman's aide. Just as often however, Jimmy would abuse the abilities of the watch, and activate it over mundane or even trivial matters. Superman has scolded him about this, and has even threatened to take the watch away should he continue to abuse it.

A similar device was actually cobbled together by Jimmy Olsen himself. This was a separate watch that he gave to his girlfriend, Lucy Lane, so she could signal him if she ever found herself in trouble. Lucy always seemed to activate it at the most inopportune time, causing Olsen great grief or embarrassment.