The valve bridge. A new method of measuring the anode impedance and voltage factor
W Baggally · Journal of Scientific Instruments · 1926
The arrangement to be described consists of an A.C. bridge; the triode under test occupying one of the arms. A standard Post Office or similar resistance box is used in the measurements, the other apparatus required being the usual A.C. source (buzzer or valve generator) and some form of detector, such as a telephone or vibration galvanometer.