Patent ID: 6633645
Filing Date: 2003-10-14
Classification: H04R

Abstract:
A hearing aid comprising:a microphone adapted to output a first signal based on an acoustic input: a voice coil pickup adapted to output a second signal based on an electromagnetic input; a signal processing circuit for processing the first signal and the second signal; and a switching circuit coupled to the microphone and to the voice coil pickup, wherein the switching circuit includes a magnetically actuated switch which energizes a voice coil circuit that includes the voice coil pickup and the signal processing circuit, and de-energizes a microphone circuit that includes the microphone and the signal processing circuit, wherein the switching circuit includes: a first transistor having a collector coupled to the microphone, a base connected to a first node, and an emitter coupled to ground; a second transistor having a collector coupled to a second node, a base connected to the first node, and an emitter coupled to ground; a third transistor having a collector connected to the voice coil pickup, a base connected to the second node, and an emitter coupled to ground; and the magnetically actuated switch having a first contact connected to the first node and a second contact connected to ground.