| 摘要 |
A method and related apparatus are provided for detecting the presence of a call waiting signal on a telephone line, where the call waiting signal is embedded in various signals. The call waiting signal frequency is isolated from the various other frequencies. The isolated call waiting frequency is then biased so that only the positive voltage portions of the signal are allowed to pass. Each positive voltage pulse as well as the zero voltage pulses are then sampled to determine whether they are representative of a biased call waiting signal. Each time a determination is made, one is added to a count on an up-down counter. When the count reaches a predetermined number, a call waiting signal is detected on the telephone line. Preferably an alarm signals the presence of a detected call waiting signal to the user. A disconnect switch interrupts a modem so that a person using the modem on the same telephone line will have sufficient time to answer a detected incoming call.
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