*The "J" switch or "Prufschalter" (test key) used for checking the 4-volt storage battery and the 120-volt anode battery as well as the 6 tubes (3xRES094), (3xRE084k) in the T3PLLä38

*Batterie = battery

*Röhren = tubes

*H = Heizspannung (heating voltage)

*S = Schirmgitterspannung = grid voltage

*A = Anodenspannung = anode or plate voltage

*With the help of the test key, the heating voltage, grid voltage, anode voltage, and plate voltage, as well as the anode or plate current in the 6 tubes, can be checked.

Photo by Bruce Culp
Photo by kind permission of the German Naval Association