The last ones I worked with were made by MedTronic, but that was a long time ago. At the time, they were in the process of miniaturizing them to something about the size of your little finger. The first ones were the size of a hockey puck.

Gary cool
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

K+E=W (Knowledge Plus Experience = Wisdom.)