Telephone ringer circuit

Claim 1

APPARATUS FOR APPRISING TELEPHONE SUBSCRIBERS OF INCOMING CALLS COMPRISING, IN COMBINATION, AN ELECTROMAGNETICALLY ACTUATED TONE STRUCTURE INCLUDING A PERCUSSION SOUNDER AND AN ARMATURE DISPOSED IN STRIKING RELATION THERETO, A MAGNETIC FLUX CIRCUIT INCLUDING A CORE FOR VIBRATING SAID ARMATURE, FIRST AND SECOND TWO TERMINAL COILS COAXIALLY WOUND ON SAID CORE, A TWO TERMINAL NETWORK WHICH EXHIBITS A RELATIVELY HIGH IMPEDANCE TO VOLTAGES APPLIED THERETO BELOW A PREDETERMINED LEVEL AND A RELATIVELY LOW IMPEDANCE TO VOLTAGES APPLIED THERETO ABOVE SAID LEVEL, A CAPACITOR DISPOSED IN SERIES WITH SAID NETWORK, MEANS FOR CONNECTING A TERMINAL OF SAID FIRST COIL TO A TERMINAL OF SAID NETWORK, MEANS FOR CONNECTING THE OTHER TERMINAL OF SAID FIRST COIL TO A TELEPHONE LINE, MEANS FOR CONNECTING A TERMINAL OF SAID SECOND COIL TO SAID CAPACITOR, MEANS FOR CONNECTING THE OTHER TERMINAL OF SAID SECOND COIL TO GROUND, AND MEANS INCLUDING SAID TELEPHONE LINE FOR APPLYING BIPOLAR ENERGY TO SAID COILS.