Importance

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Abstract

Transient signal elimination circuitry is disposed in a local communications loop extending from a subscriber telephone to a telephone central office couples ringing and on-hook and off-hook signals through the loop after removing transients in these signals. The circuitry also isolates the telephone subscriber and central office from the local loop until an off-hook signal is detected and restores this isolation when an on-hook condition exists at the telephone subscriber. Transient signal elimination is accomplished with a CPU driven interface which detects undesirable transients such as a ringing or off-hook signal, and in response thereto generates a burst of double tone signal to alert connected equipment. In this manner, the local loop can be simultaneously used for both voice communications and a second information signal with each signal capable of occupying the same bandwidth. These signals can operate independently of each other.

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First Claim