PROTECT YOUR VALVES

Radio Record, Volume I, Issue 42, 4 May 1928, Page 3

PROTECT YOUR VALVES

1 Ilome-builders, experimenters, and others can prevent their valves fron being burnt out by accidental contact of the B battery circuit with the filament circuit of their valves by meaus of a simple device. The device cousists of an ordinary 4U-watt clectric light placed in series with the ncgative B battery. le filament of the lamp, when cold, offers but Jittle resistance. Wheti an excessive cutrent drain is placed on the cirenit the filament heats up and thereby increases tire registance of the leinp a great number of times. When the set is operating properly the lamp does not burn. Whenever a short is placed on the B battery the lamp lights up, thereby warning you that a short citcuit has eccurred, and. at the same time the amount of curtrent in the circuit is limited, aud your yalyes are protected. In actual operation the lamp may be short-cir-cuited if you desire, but it should always be used in trying out a new Circuit, or in making changes ML your | present circuit.