Device for generating a visual display in response to a varying magnetic field

Abstract From the Canadian patent

A device which converts the magnetic field of an electrical bell call signal of a telephone receiver to an electrical lamp display and discriminates such signal from the varying magnetic field generating by a dialing action of the same receiver. A direct conductive electrical connection of the device to the receiver is made unnecessary by an inductive sensor associated with an amplifier. A time-delay circuit provides discrimination, and a ring counter circuit provides the desired sequential operation of the display lamps. An additional connection may be provided leading to a remote optical or acoustic indicating device which is operated by the first device.