It's useful troubleshooting old radios. You can find the manual here:

http://web.archive.org/web/20020201194744/http://www.circuitarchive.co.uk/heath.htm

Norm

:My son found a working IT-12 (Heathkit Signal Tracer) at a yard sale. He bought it thinking that I might be able to utilize it when fiddling with some of the old tube gear.
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:Does anyone have experience using these things? Is it a good, useful tool?
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:Thanks
:Bill