In normal operation the screen grid is connected to a positive DC voltage slightly less than the plate voltage, and bypassed to the cathode with a capacitor, so it was at AC ground. To take full advantage of the very low internal grid-anode capacitance, the valve must be used in circuits in which the shielding between anode and grid is continued externally. In the case illustrated (S625), the valve was intended to be inserted into a hole in an external, grounded, sheet-metal shield aligned to correspond with the position of the internal screen-grid. The input, or control-grid circuit was on one side of the shield, while the anode, or output circuit was on the other. In the case of the Osram Music Magnet, each entire stage of the 2-stage rf amplifier, as well as the tuned detector stage, was enclosed in an individual large aluminium screening box. These boxes have been removed in the illustration, but the up-turned edges of the bases of the boxes can be seen.