An electromechanical striker used in early spark-gap radio receivers to physically tap a coherer tube. When an incoming radio frequency signal caused the metal filings inside the coherer to clump together and conduct electricity, the tapper would strike the glass tube to break the filings apart, restoring their high electrical resistance and readying the receiver for the next Morse code dot or dash.
Heard on the job
The receiver failed to pick up the second character because the tapper stuck and didn't decohere the filings.
Also heard as
- decoherer