We've got this old kearny & trecker mill, it's so old, the serial number is "2". anyhow, I keep getting a "spindle tachometer overload" message, which kills my spindle mid-pass (thankfully, my feed too) anyone know how to bypass this sensor? I'm told it needs to be cleaned, but this happens more and more frequently after cleaning, so can it be safely bypassed?
Since I'm on the K&T subject, does anyone know what FXC means? I have to put this in every time I change an offset, but I don't know why... it ends up looking like this...

(FXC,H1X0)
H1

cycle start x 2

(FXC,H1X[machine reference no.])
H1

Cycle Start x2

I know how to do it, I'm just curious as to why I have to do this...