[bbarn]

For cadence and speed, they are very rarely "wired" anymore. Almost all use ANT+ for communication, it's a very low power protocol meant for low power usage.

Electronic shifting (Other than SRAM's newest) is however wired, but again it's a very low power protocol. It also uses two motors to perform the shifts, but they are very small and external.

I would imagine you could tell the difference and find what you're looking for with something as simple as this: http://www.amazon.com/Fluke-LVD1-Volt-Light/dp/B000B64ZDG

I used to use one for electrical work, and it worked very well.