Device and method for determining tone ringing frequency

The invention relates to a voice-frequency ringing rendering determining method, comprising the following steps: Is connected with a lower threshold value (S) and voice-frequency ringing signal of the voice-frequency ringing signal and a ZC signal, the ZC with signal between two ZC signal values alternating the raising of changes along and drop in sequence,Said of the raising of ZC of signal and voltage in the middle of the duration; The duration for a determine compares the predetermined duration limiting value (tg); The duration for determining is greater than or equal of the duration limiting value (tg), an estimating parts time, evaluating comprises a time the lower edge; timeWith the same ZC signal value duration for and a lower determine time is greater than or equal to the duration limiting value (tg), an estimating adjunct time, evaluating adjunct time of the lower edge; timeAnd a second for determining evaluating adjunct time and evaluation adjunct time between the differential value determining frequency (f).