Patent ID: 8204212
Filing Date: 2012-06-19
Classification: H04M

Abstract:
1. A method for reducing noises in a subscriber line interface circuit (SLIC) of a phone, the SLIC comprising a surveillance module, a control module and a register, the method comprising: detecting a work state of the phone using the surveillance module, wherein the work state comprising an on hook state, an off hook state and a pulse dialing state; reading a voltage on hook on the tip wire using the register when the surveillance module detects the phone is in the on hook state; reading a voltage off hook on the tip wire and a voltage off hook on the ring wire using the register when the surveillance module detects the phone is in the off hook state; and in response to the surveillance module detecting the phone to be in the pulse dialing state, calculating a public voltage based on the voltages in the register using the control module and loading the public voltage on the ring wire to convert oscillatory voltages on the ring wire to symmetric wave forms having phases opposite to those on the tip wire.