Patent ID: 7428304
Filing Date: 2008-09-23
Classification: H04M

Abstract:
1. A non-echo canceling voice band modem capable of detecting subscriber alerting signal (SAS) tones and customer premises equipment alerting signal (CAS) tones, said modem comprising: a shaping filter in a transmitting path of said modem for filtering signals to be transmitted from said modem; an analog-to-digital converter (ADC) in a receiving path of said modem for converting incoming signals; a SAS tone detector; a CAS tone detector; and an echo canceler coupled to said SAS and CAS tone detectors, wherein said echo canceler cancels echoes in modem signals before sending said modem signals to said SAS and CAS tone detectors, wherein said echo canceler includes a high-pass filter, a low-pass filter, an adaptive filter and a summing circuit, wherein said adaptive filter and said summing circuit are utilized in conjunction with said low-pass filter to provide a first error signal for said SAS tone detector when said modem is operating in an originate mode.