| 摘要 |
A system for use in detecting whether one of the parties to a telecommunication has attempted to initiate a three-way call using a hook-flash signal. The apparatus includes a low pass filter (12) for passing energy having frequencies below about 500 Hz, and an energy detector (16) for detecting a specific electrical energy pulse characteristic of the hook-flash having passed through the low pass filter. The existence of the hook-flash is confirmed by digital signal processing equipment (18) which identifies a rapid drop-off in energy also characteristic of the hook-flash signal. Optionally, the hook-flash may be further confirmed by including software for cooperating with the energy detector to ascertain whether sound has occurred in the communication during a predetermined period following the first hook-flash signal. |
