21 [ ELECTRIC WAVE FILTERS, ELECTRIC EQUALIZER FILTERS, POWER TRANSFORMERS, INPUT TRANSFORMERS, AUDIO TRANSFORMERS, OUTPUT TRANSFORMERS, INTERSTAGE TRANSFORMERS, BRIDGING TRANSFORMERS, LINE TRANSFORMERS, POTENTIAL TRANSFORMERS, CURRENT TRANSFORMERS, PULSE TRANSFORMERS, IMPEDANCE TRANSFORMERS, FILTER CHOKE COILS, REACTOR COILS, INDUCTOR COILS, ] TELEPHONE PLUGS AND TELEPHONE JACKS