Abstract: A non-echo canceling voice band modem capable of detecting subscriber alerting signal (SAS) tones and customer premises equipment alerting signal (CAS) tones is provided. The modem includes a shaping filter, an analog-to-digital converter (ADC), a SAS tone detector, a CAS tone detector and an echo canceler. The shaping filter, which is located in a transmitting path of the modem, filters modem signals to be transmitted from the modem. The ADC, which is located in a receiving path of the modem, converts any incoming analog signal to corresponding digital signals to be used by the modem. The echo canceler, which is coupled to the SAS and CAS tone detectors, cancels any echoes in modem signals before sending said modem signals to the SAS and CAS tone detectors.

Abstract: A non-echo canceling voice band modem capable of detecting subscriber alerting signal (SAS) tones and customer premises equipment alerting signal (CAS) tones is provided. The modem includes a shaping filter, an analog-to-digital converter (ADC), a SAS tone detector, a CAS tone detector and an echo canceler. The shaping filter, which is located in a transmitting path of the modem, filters modem signals to be transmitted from the modem. The ADC, which is located in a receiving path of the modem, converts any incoming analog signal to corresponding digital signals to be used by the modem. The echo canceler, which is coupled to the SAS and CAS tone detectors, cancels any echoes in modem signals before sending said modem signals to the SAS and CAS tone detectors.

Abstract: A method and apparatus for improving upstream connect rates of an analog modem are provided. The analog modem includes a modem transmitter, a modem receiver, a transmitter re-sampler, a receiver re-sampler and a codec. A sampling rate converter is provided between the modem transmitter and the transmitter re-sampler. The sampling rate converter changes the input sampling rate to the transmitter re-sampler by a factor equal to the ratio of the sampling rate of analog modem codec to the symbol rate of the modem transmitter in order to avoid attenuation in the transmitter re-sampler. The transmitter clock is synchronized with the codec sampling clock in a central office. The transmitter re-sampler corrects the clock difference between the sampling clocks of modem codec and central office codec.

Abstract: A method and apparatus for synchronizing a transmitter clock of an analog modem to a codec sampling clock within a central office are provided. The analog modem includes a transmitter, a receiver and a codec. The analog modem also includes a transmitter re-sampler and a receiver re-sampler coupled to the transmitter and the receiver, respectively. Transmitter signals provided to the codec in a transmit path of the analog modem are re-sampled. The sampling rate of the transmitter re-sampler is subsequently derived from a re-sampling period of the receiver re-sampler provided between the receiver and the codec. The transmitter clock of the analog modem is then synchronized with the codec sampling clock in the central office.