A recent post makes me curious.
Diesel-Electric locomotives have isolation switches which can be used from the cab -- regardless of whether the locomotive is stationary or moving -- to prevent or allow the individual locomotive unit to produce power.
Also, most diesel-electrics built since the 1960s have traction motor cutout switches which allow one traction motor on a 4-axle locomotive, or a pair of motors on a 6-axle locomotive, to be isolated (i.e., to cut of power to the motor[s] typically due to a high voltage ground fault).
Did the Pennsylvania Railroad GG1 electric locomotives have switches that performed those functions, which could be positioned by the Engineer or Fireman if necessary while en route?
(I realize that the pantograph could be lowered to cut off everything, but there were other situations in which such a heavy handed solution might not be the answer, when some electrical power for other than traction would be needed, such as train heating steam generator, control circuits if the particular GG1 was the controlling locomotive in a consist, lights, air compressor, etc.)