- Flame proof straight key of US Signal Corps.
Similar to J-5-A flame proof key yet equipped with a
"winker light". The latter was loosely coupled to
the aircraft transmitter output to provide for visual
indication in noisy environment of the airplane. The flame
proof keys of J-5/J-6/J-7 family were used to operate
spark-gap transmitters in hazardous environments like
aircraft cabin filled with fuel perspirations. These keys
were in use during and after WW1. Our sample was made by
L.S.Brach Mfg.Co. of Newark, New Jersey, in 1921.