P= R1=consists of ratio  dials of 1, 10, 100 and 1000 ohms

R2=consists of ratio  dials of 1, 10, 100 and 1000 ohms

C1 = Gang Capacitor of 500pf.

Q = in this arm C1 is placed parallel with R2 to form 2nd   arm cd

R = C3= consists of three dial condenser box of 0.001x10, 0.01x10 & 0.1x10mfd.

R = consists of three dial resistance box of 1x10, 10x10, 100x100 ohms.

unknown Capacitor C1 whose value is to calculated is connected in series with r to form 4th arm S

Terminal for headphone, unknown capacitor & oscillator for provided.