JPS6254277B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system for shaping the waveform of a dial pulse sent from a terminal in a switching device.

Conventional dial pulse waveform shaping methods generally use relays. In this method, the telephone dial pulse signal was sent out at a duty rate of approximately 30% so that the waveform after shaping would have a duty of 50%, taking into consideration the waveform distortion caused by the difference between the relay's operation delay time and recovery delay time. . In this kind of method,
Since it uses a relay, it has the disadvantage that it cannot be made smaller.

In response, several attempts have been made to realize similar functions using electronic circuits (for example, Proceedings of the 1985 National Conference of the Institute of Electronics and Communication Engineers, Paper No.
397, Usuda et al. “Subscriber circuit for digital exchange
``IC''), a large capacitor is required, and in order to obtain the desired time accuracy, a highly accurate capacitor and resistance value is required, which cannot be incorporated into an integrated circuit, and the input waveform and shaping In order to change the duty depending on the subsequent output waveform, a time constant changing means for individually setting the charging/discharging time is required, which has the disadvantage of complicating the circuit.

In order to eliminate these drawbacks, the present invention controls an up-down counter depending on the presence or absence of current in the communication line, and controls the up-down counter when the counted value of the up-down counter reaches a predetermined value, for example, a constant value or zero. When determining the presence or absence of current in the telephone line and counting the counter, separate clocks are used for incrementing and decrementing the count value, thereby making it possible to distinguish between the input waveform and the output after shaping. The present invention provides a dial pulse waveform shaping method that can flexibly handle cases where waveform duties differ, is suitable for integrated circuits, and is not affected by noise or chatter.
Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which CNV is a dial pulse waveform shaping circuit according to the present invention;
TEL is the contact point of the dial at the end of the telephone, L _A , L _B
is the communication line, A and B are the output terminals of the switching center, DET
indicates current detection means. CTR of the dial pulse waveform shaping circuit CNV is an up-down counter, U is an up control input, D is a down control input,
C is clock input, Q _o is n count output, ALL
“0” is an output terminal when all are zero. or,
FF is a flip-flop, S is a set input, R is a reset input, and Q is a flip-flop output. AND1 and AND2 are AND circuits with inhibit terminals, INV is an inverting circuit, and OR is an OR circuit.
SCN IN, SCN OUT, CLK1, and CLK2 are the input or output terminals of the dial pulse waveform shaping circuit CNV, where SCN IN is the dial pulse input terminal, SCN OUT is the shaping output terminal, and CLK1 is the clock signal for increasing the count value. Input terminal, CLK2
is a clock signal input terminal for decreasing the count value.

FIG. 2 is a timing diagram for explaining the operation of FIG. 1, and symbols similar to those in FIG. 1 represent waveforms of corresponding portions. In FIG. 2, the waveform part a represents the chatter of the dial contact of the telephone terminal,
The waveform part b represents unnecessary pulses due to noise,
The waveform portion c represents waveform cracking due to noise. SCN IN is the detection output waveform of the current detecting means DET of the current flowing in the communication line, and the symbol written with a bracket after CTR and FF is an up-down counter.
Waveforms of each terminal of CTR and flip-flop FF,
(CTR) is the count value of the up-down counter CTR.

Next, the operation shown in FIG. 1 will be explained with reference to FIG. By intermittent operation of the dial contact TEL at the end of the telephone, the telephone line L is connected by the power supply E.
Intermittent current flows through _A and _LB. The intermittent current is detected by the current detection means DET and converted to a logic signal level, but the waveform includes chatter etc. as shown by SCN IN in Fig. 2, and is sent to the dial pulse waveform shaping circuit CNV. is input. The input signal
When SCN IN is “1”, that is, current is flowing through the communication lines L _A and L _B , the up-down counter
CTR is controlled to the up side, and the input signal SCN IN
is “0”, that is, when no current flows in the communication lines L _A and L _B , the up-down counter CTR is
Controlled down side through INV. and circuit
The first input of AND1 is the input signal SCN IN, the second input is the clock signal CLK1, the inhibit input is the signal when the count value of the up-down counter CTR reaches a constant value Q _o , and the first input of the AND circuit AND2 is input. The input is an inverted signal of the input signal SCN IN, the second input is the clock signal CLK2, and the inhibit input is a signal when the count value of the up-down counter CTR becomes zero. The outputs of the AND circuits AND1 and AND2 are logically summed by the OR circuit and used as a clock input signal for the up-down counter CTR. When the count value of the up-down counter CTR reaches a certain value, the flip-flop FF is set and the clock input signal for the up-down counter CTR is set.
Flip-flop occurs when the count value of reaches zero.
Reset FF. Then, the Q output of the flip-flop FF is set as the waveform shaping output SCN OUT.

Now, if the input signal SCN IN is “0”, CTR
Since (U) becomes "0" and CTR (D) becomes "1", CTR is controlled down. in this case,
The first input of AND1, that is, SCN IN becomes "0", and the clock signal CLK1 of the second input of AND1 becomes "0".
is not output, while the first input of AND2, i.e.
The inverted signal of SCN IN becomes “1”, and the inhibit input of AND2 becomes “0” because the count value of CTR is not zero.
and the clock signal of the second input of AND2
CLK2 is inputted to the C terminal of CTR through an OR circuit, and CTR counts the count value in a decreasing direction by clock signal CLK2. In this way, CTR
is counted until the count value of the CTR reaches zero, and when the count value of the CTR reaches zero, the ALL “0” terminal becomes “1”, and as a result, the inhibition input of the AND2 becomes “1”. The clock signal CLK2 of the second input of the AND2 is not output, the CTR stops the counting operation, and the R terminal of the FF becomes "1", the FF is reset, and the output of the FF, that is, the waveform shaped output. SCN OUT becomes “0”. This state is maintained until the input signal SCN IN becomes "1".

Input signal of dial pulse waveform shaping circuit CNV
When SCN IN changes to “1”, CTR(U) becomes “1” and CTR(D) becomes “0”, and CTR
becomes up control. In this case, the first of AND2
The inverted signal of input SCN IN becomes “0”, and the corresponding AND
The clock signal CLK2 of the second input of AND1 is not output, while the first input SCN IN of AND1 is "1", and the inhibit input of AND1 is "0" because the count value of CTR has not reached a certain value. ” and applicable
The clock signal CLK1 of the second input of AND1 is inputted to the C terminal of CTR through an OR circuit, and CTR counts the count value in an increasing direction by the clock signal CLK1. The CTR counts the clock signal CLK1 until the count value reaches a constant value _Qo , and when the count value of the CTR reaches the constant value, its _Qo output becomes “1”.
As a result, the inhibit input of the AND1 becomes "1", so the clock signal CLK1 of the second input of the AND1 is not output, the CTR stops counting, and the S terminal of the FF becomes "1". ” became the FF
is set, and the output of the FF, that is, the waveform shaping output SCN OUT becomes "1". This state is maintained until the input signal SCN IN becomes "0".

According to the configuration shown in FIG. 1, the clock for increasing and decreasing the CTR count value is divided into an increase clock CLK1 and a decrease clock CLK2, so that the increase time and decrease time of the CTR count value are Can be set individually. Therefore, it is possible to flexibly deal with the case where the duty is different between the input waveform and the output waveform after shaping. In addition, noise pulses b that occur when noise is induced in the communication lines L _A and L _B , or unnecessary pulses a or waveform cracks c that occur due to the chatter of the telephone dial contact TEL.
On the other hand, if the frequency of occurrence or duration varies depending on whether the communication current is present or not, the time required for the counter of the operating state where the occurrence frequency or duration is high to reach a predetermined value is lengthened. In other words, by lengthening the clock period, unnecessary pulses,
The protective effect against disuse in the case of waveform cracking can be set arbitrarily, and the waveform shaping of dial pulses with stable operation can be performed.

In the above explanation, the up-down counter
Although I did not mention the internal configuration of the CTR, its configuration method is well known, and the AND circuit
AND1, AND2, the inverting circuit INV, etc. can be combined with the gate circuit etc. constituting the up-down counter CTR, and the present invention is not limited by their configuration. Also flipflop
Up-down counter when resetting FF
Although the CTR count value is "0" as an example, it is not limited to this, and may be any other value smaller than _Qo .

As explained above, the present invention does not use large capacity capacitors or high-precision resistors, and is constructed with a digital circuit, so it is suitable for integrated circuits and provides a compact, economical, and highly accurate dial pulse waveform shaping circuit. Moreover, when counting the up-down counter, separate clocks are used for incrementing and decrementing the count value, so it can flexibly handle cases where the duty is different between the input waveform and the output waveform after shaping. It also has the advantage of eliminating noise, unnecessary pulses due to chatter, and waveform distortion.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a timing chart for explaining the operation of FIG. 1. TEL…Dial contact of telephone terminal, L _A , L _B
...Talking line, A, B...Exchange terminal, DET...
Current detection means, E...DC wire, CNV...dial pulse waveform shaping circuit, CTR...up-down counter, FF...flip-flop, INV...inverting circuit, AND1, AND2...AND circuit with inhibit input,
OR...OR circuit, SCN IN...Waveform shaping circuit input signal input, CLK1...Addition clock input, CLK2
...Clock input for subtraction.

Claims (1)

[Claims] 1 In a dial pulse waveform shaping method that inputs a dial pulse signal sent from a telephone via a telephone line and shapes it into an output signal with a duty different from that of the dial pulse signal, cases in which the count value increases and cases in which it decreases The up-down counter circuits each use a different clock, and depending on the presence or absence of an intermittent current signal flowing through the communication line, the count value of the counter circuit is switched in the direction of increasing or decreasing to count the clocks, and the count value is A dial pulse waveform characterized in that when a predetermined first value is reached, a current is present in the telephone line, and when a second value is reached, there is no current in the telephone line. Plastic surgery method.