Device and method for determining tone ringing frequency

Ringing-Freguenzbestimmungsvorrichtung and procedures

STATE OF THE ART

The present invention relates to a tone ringing frequency determining means and a corresponding tone ringing frequency determination method.

Although applicable to any Tonrufsignalisierungen, the present invention and the underlying problem with respect to a ring tone signaling are explained for a home phone.

To ensure error-free signaling of the ringing tone, certain demands are placed on a Ringer tone. On the one hand is to start after a certain Mindestaussteuerung (level condition), on the other hand (condition frequency) only suggestions at a fixed frequency window, carried a signaling.

Compliance with the level condition is guaranteed by the rule of the hardware, the compliance with the frequency condition, however, is the object of the software. Failure to comply with one or both conditions may cause incorrect call signaling (eg absence or late in signaling a valid call signal, call signal without ringing voltage, ETC.

have Superimposed interference of the ringing alternating voltage has a great influence on correct functioning of the ringer frequency detection. However, recognizing disturbed frequencies is not a trivial problem.

Fig. 3 shows an illustration for deriving a signal ZC (ZC = Zero Crossing) from the detected voltage Tonrufspan-.

In Fig. 3, the time t on the x-axis is applied and the TonrufSpannung U_τ or the ZC-ZC Ξignal on the y axis. The TonrufSpannung U_τ in this case as a pure sine echselspannung (solid line in Fig. 3 above) was adopted.

To allow a ringing frequency identification, is the rectified TonrufSpannung U_τ (Dashed line in Fig. 3 above) is applied to a comparator, not shown. The output of the comparator is connected to a processor which processes the ZC signal.

As shown, the comparator performs a comparison of the rectified TonrufSpannung U_τ with a threshold S by. Every time the rectified TonrufSpannung U_τ this threshold by running uphill, the ZC signal has a falling edge. Each subsequent Nulldurch- gang has the ZC signal a rising edge. Here, then, some hysteresis is built.

The frequency f of TonrufSignals results in this simple case, when t * = l / 2f, where t^* the time interval between two successive rising or falling edges of the ZC signal.

Fig. 4 shows an illustration of a ZC signal without disturbance with different amplitude of TonrufSignals.

As Fig. 4 can be removed, depending on the location of the comparator threshold S or signal swing of Tonrufsignals the duty cycle of the ZC signal greatly.

However, in order to measure the period or frequency f, is usually always triggered on the rising or falling edge of the ZC signal, a determination of the frequency f is independent of the duty cycle of the ZC signal possible.

In real systems, it must be expected that the ring signal is not a pure sine wave, but has periodic and / or aperiodic overlays. These overlays make particularly noticeable when the amplitude of the disturbance is greater than the hysteresis of the ZC-detection circuit. A measure of the resistance to such interference is the external signal immunity. A superimposing noise on the ZC signal results in waveforms shown in Fig. 5 for a disturbed ZC signal with varying duty cycle.

A quick as possible evaluation of such disturbed ZC- signals is not trivial. To determine the fundamental, the interference must be ignored. In an unfavorable duty but glitches and useful signal are indistinguishable.

Systems are known, hide the pulses or pulse groups. These have one hand the disadvantage that additional resources before (eg second time base of the Blend

Disorders) are required. On the other hand, such systems take actually a kind of sub-sampling of the ZC signal by blanking a specific time period before. Is this the hidden time interval, compared to the measured times, no longer negligible, occur measuring errors.

This is illustrated in Fig. 6, which Error Anti-jamming of the ZC signal showing that arise by simply hiding the faults. The collapsed time range is shaded gray. T_M referred to the measurement interval.

In case a) of FIG. 6 there is a ZC signal without interference that Tonruffrequenz f is determined correctly. In case b) of Fig. Β there is a ZC signal with interference that Tonruffrequenz f is properly determined.

In case c) of Fig. 6 is located in front of a ZC signal without interference that Tonruffrequenz f is not correctly determined, since parts of the useful signal are incorrectly hidden. In other words, an undisturbed invalid signal is erroneously determined to be valid.

One disadvantage with the above known approaches, so the fact it has been found that a reliable fix is ​​not in all cases is possible.

ADVANTAGES OF THE INVENTION

The inventive determining tone ringing frequency method with the features of claim 1 and the corresponding determining tone ringing frequency apparatus according to claim 5 further sen compared to the known solutions have the advantage that, in spite of high-frequency disturbances on the ZC signal a reliable noise suppression is possible in contrast to known Ausblendverfahren ,

The the present invention underlying idea is that each time interval is evaluated between a falling and rising edge of the ZC signal and determined by a limit a Bewertungsstart- and evaluation stop time, said he it- Review-switched interval is a measure of the desired frequency.

In the subclaims fertilize advantageous refinements and improvements of the subject invention in question.

According to a preferred development, a monitoring time window is set for the frequency determination and done a cancel the measurement, if the measured since the evaluation start time period outside the monitoring time window is.

According to a further preferred development of the time-limit is set as a constant.

According to a further preferred embodiment, a maximum value is set for the time-limit, with the attempt of establishing the evaluation start time will indulge described. This value is reduced according to a predetermined algorithm, if after a certain time no evaluation start time can be secured.

DRAWINGS

Embodiments of the invention are illustrated in the drawings and erläuter detail in the following description. Show it :

Figure 1 is an illustration of one embodiment of the inventive method as applied to a disturbed ZC signal with varying duty cycle.

Fig. 2 is a state diagram of the embodiment of the inventive method according to Fig. 1;

Figure 3 is an illustration for deriving a ZC signal (ZC = Zero Crossing) from the detected TonrufSpannung.

Figure 4 is an illustration of a ZC signal without interference with different amplitude of Tonrufsignals.

Figure 5 is an illustration of a disturbed ZC signal with varying duty cycle. and

Fig. 6 is an illustration of the problem, which Error Anti-jamming of the ZC signal by simply blanking the the disorders arise. DESCRIPTION OF THE EMBODIMENTS

In the figures, like reference numerals designate identical or functionally identical components.

Fig. 1 shows an illustration of an embodiment of the method according to the invention as applied to a disturbed ZC signal with varying duty cycle.

In this embodiment of the inventive method for determining the fundamental not single time ranges will be ignored, but takes into account all partial events. Here, it is assumed that the disorders which are the ZC signal superimposed high frequency than the frequency to be determined are f.

In other words, a constant measuring the respective time duration between the adjacent rising and falling edges of the ZC signal takes place. From these ratios Teilereig- the frequency of the fundamental oscillation is then derived. The embodiment assumes that the direction of the edge (falling or rising) of the ZC signal can be successively converted to generate an interrupt.

The duration of the individual partial measurements m_x, M, be a predetermined constant threshold in this example t_G compared. Is the time duration of a Teilmes- εung greater than the limit value T_G, The start condition is present, ie a review start time t_x set, if a measured time duration is greater than or equal to the time duration limit value t_G is the evaluation start time (t) is the time of the following edge. At the same time the phase of the ZC input signal will be determined ( "0" = l (ow) or "1" = h (igh)). In Fig. La) and lb), this phase position is "0", and in Fig. Lc) is "1".

The stop condition is over the next long ZC-cycle signal with the same phase position. So there is a valuation stop time t₂ established when a measured time duration with the same ZC signal value to the next time is greater than or equal to the time duration limit value t_G is the evaluation stop time t₂ the timing of the subsequent edge.

The timer or clock, from which all times are derived runs freely after the start condition. The time required for the timer for a run, must be greater than the Uberwachungsfenster for the ZC signal by a lower time limit T_u and an upper limit time T₀ can be defined.

If no other interrupts detected in this Uberwachungsfenster, the measuring process is aborted and the measurement function back to their initial state (ie, the frequency is very small). Determining the frequency f this happens based on the measured time difference between the evaluation start time i and the evaluation stop time t₂, Where 1 / f = t₂ - t_x ,

For the determination of t_G functional parameters are for example:

Comparator threshold a (V_on) 17.5 V

Comparator threshold of (V_off) 6.5 V minimum frequency (f_mln) 20 Hz maximum frequency (f_Max) 60 Hz

Interference voltage (U_Sτ) β V_s

Ringing voltage (U_R) 32 V_eff

Fig. 2 shows a state diagram of the embodiment of the method of FIG. 1.

In Fig. 2, I denotes an initialization to enable the system to a ground state G. Assuming the time interval between the adjacent rising and falling edges of the ZC signal is measured until an interval equal to t with t greater_G is found.

Then the timer for an evaluation start time ti is started (START), which is the date of the following edge.

For evaluation stop time t₂If a measured time duration with the same ZC signal value to the next time is greater than or equal to the time-limit t_G is the evaluation stop time t₂ is the date of the following edge, the timer is stopped again.

The various time points at which a measured time duration is greater than or equal to the time duration limit value t_G is, are designated with I, II and III. Loop left is for the case of L-initial phase, the right in the case of H-initial phase. The respective loop designated 1) means that either the time or the phase condition is not satisfied.

Is the measured time interval T is within the allowable time window [T_U, T₀] Who determined therefrom frequency f is valid, and the system returns to the ground state G. Otherwise, the system goes back to state I.

Although the present invention has been described above with reference to a preferred embodiment, it is not limited thereto but can be modified in many ways.

The parameter t_G can be fixed with small ranges as constant as in the above example. The time intervals of the undisturbed signal component with highest valid frequency f_Max be as t need greater_G, For larger measuring ranges and constant ZC input signal (ie, the frequency does not change during the measurement), measurement with maximum t_G be started. If no Start condition found, the parameter t_G decreased until a start condition is found.