new ones usually say on them, at least if they're internally resisted they say 'not for use with external resistor' - if it's an original from before the 60's it'll be for use with the resistor

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot