JPH0453158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an incoming call detection method for determining and detecting incoming calls from a central office line based on a ringing signal.

In recent years, interface circuits such as central office line trunks have
As IC packaging is progressing, there is a demand for smaller calling signal detection circuits.

FIG. 14 is a block circuit diagram showing a schematic configuration of a central office line trunk including this type of paging signal detection circuit. In the same figure, central office trunk (TK) 1
32 is provided in the private branch exchange (PBX) 131 and forms an interface circuit between the central office line MW from the central office (CO) 130 and the private branch exchange 131. The office line trunk 132 includes a ringing signal detection circuit (R) 137, a loop monitoring circuit (M) 136, and a hybrid circuit (HYB) 135. 2
Switch A ₀ provided on the wire-type communication line l ₁ is for sending dial pulses, and switch B ₀ is for creating a loop. Hybrid circuit 135 has 2 wires -4
It is a line conversion circuit that converts the signal on the two-wire bidirectional communication line _L1 to the exchange switch 1 via the two-wire communication line _L2 .
33, and the signal from exchange switch 133 is transferred to the communication line _l1 via the two-wire communication line _l3 .

Normally, when a private branch exchange 131 is connected to the central office exchange 130, an interface similar to that of a general subscriber is used.
A paging signal is then sent to the corresponding station line MW. The ringing signal detection circuit (R) 137 of the trunk circuit 132 on the exchange 131 side detects this ringing signal and connects the signal line.
l ₄ , and notifies the central controller (CC) 140 via the scanning circuit (SCN) 139. The central control unit 140 detects a paging signal from the signal line _l4 and performs incoming call processing to a switchboard in the exchange 131, an extension subscriber, etc. After the switchboard, extension subscriber, etc. respond, the signal distribution circuit (SD) transfers the relay drive signal to a call and normal switching operation via signal lines _L5 and _L6 .
138, drive the relay through signal lines l ₅ and l ₆ ,
Switch switch A ₀ and switch B ₀ . The loop monitoring circuit (L) 136 monitors whether or not a DC loop is formed on the communication line _l1 , and sends the loop formation status to the central control unit 140 via the signal line _l8 and the scanning line 139. , to detect call interruptions, etc. on the central office line side.

When a call is made to the central office 130 from the subscriber telephone TEL, the central control unit 140 uses an off-hook operation to call the subscriber circuit (LNC) 13, for example.
When the call is detected through the switch A 0 , and the incoming call is detected by the receiving dial, the switch A ₀ is activated.
B ₀ is closed, and then the called party's dialing signal is sent to the called party by repeatedly turning switch A ₀ on and off under the control of central controller 140. For example, the central controller 140 has a memory (M) 141
Incoming call control in such an exchange system under program control is performed by detecting level fluctuations due to the calling signal in the calling signal detection circuit 137.The conventional incoming call detection method will be specifically explained below.

[Conventional technology]

FIG. 15 shows an example of a conventional calling signal detection circuit. FIG. 16 is a waveform diagram for explaining the operation of the conventional circuit shown in FIG. 15. 15 and 16, when a low frequency calling signal A as shown in FIG. 16A is sent from the office line MW, the photocoupler P1 detects the positive potential part of the calling signal and the photocoupler _P1 detects the positive potential part of the calling signal. _P2 detects the negative potential portion of the ringing signal. However, near the zero crossings of the calling signal Z ₀ , Z ₁ ,
Since the voltage is too low at Z ₂ ,..., the photocoupler
P ₁ and P ₂ cannot detect the positive voltage or negative voltage in this part and are undetectable. Therefore, a comb-shaped waveform as shown in FIG. 16B is obtained at the output B of the photocouplers _P1 and _P2 . In FIG. 16B, a 0V portion indicates a period in which the photocoupler P ₁ or P ₂ is moved and conductive, and a +5V portion indicates a period in which both photocouplers P ₁ and P ₂ are not moved and conductive.

Conventionally, the waveform shown in FIG. 16B was integrated by an integrating circuit consisting of a resistor R and a capacitor C, and the output C had a waveform as shown in FIG. 16C. The central control unit 140 periodically scans the output of the calling signal detection circuit R ₀ and considers that a calling signal has been detected if the output voltage is below a predetermined threshold. FIG. 16D shows the calling signal as a detection signal of "1" and "0" information through the scanning circuit 139. When it is "0", the calling signal is detected, and when it is "1", the calling signal is detected. No signal detected.

[Problem that the invention seeks to solve]

As mentioned above, the conventional calling signal detection circuit _R0 includes an integrating capacitor C. However, since the frequency of the calling signal is generally low (for example, 16 Hz in Japan), the time constant of the integrating circuit must be large, and therefore the capacitance of the capacitor C must be relatively large. These large capacity capacitors are large in size and can be used in central office trunks.
This is an obstacle for IC package. Furthermore, when the frequency of the calling signal is changed, the time constant must also be changed, which causes the problem that the capacitor must be replaced.

[Means for solving problems]

In view of the above-mentioned problems in the conventional circuit, the present invention removes the integrating circuit from the ringing signal detection circuit, samples the output voltage of the voltage detection element periodically in its place, and prevents changes during sampling within a fixed period. By determining that a ringing signal has arrived based on the ratio of the number of detections at a predetermined level, the use of a capacitor in the ringing signal detection circuit becomes unnecessary, thereby reducing the circuit requirements and improving the IC package of the central office line trunk. In addition to making it easier to
To provide a calling signal detection circuit that does not require changing hardware even if the frequency of the calling signal changes.

FIG. 1 is a schematic configuration of a system for explaining the outline of the present invention. Although the exchange control operation is not different from that shown in FIG. 14, it is shown as an example of distributed control. A trunk circuit 100 for a central office line interface is provided between the central office exchange CO and the exchange switch ( _NW ) 111 of the private branch exchange. 108 and is detected by the control unit (CPU) 104 via the scanning circuit 107.
It is recognized by The ringing signal detection circuit 108 is configured to simply detect voltage changes, and in the present invention, the control device 104 detects changes in the signal level in short cycles, and calculates the rate of change within a certain period of time. Therefore, it is designed to detect whether or not there is an incoming call. In this example, the signal level ratio is determined by program control of the control device, but it may also be detected by providing a simple majority circuit within the calling signal detection circuit. Furthermore, the detection method of the present invention is as follows:
Although this may be done in the central control unit of FIG. 13, the sampling process for detecting the calling signal is added, which puts pressure on other switching control processes. Therefore, it is optimal to perform the processing in the control device in each trunk package in distributed control.

[Effect]

In the present invention, the output of the level detection conversion circuit such as the voltage detection element is directly controlled by a device (or majority decision circuit).
The detection level is counted within a certain period of time, and the ratio corresponds to the ratio of the paging signal level, making it possible to detect an incoming call.

〔Example〕

First, the overall configuration of an exchange system according to the present invention will be explained with reference to FIG. Inside the trunk circuit 100, there is a ringing signal detection circuit (R ₁ ) 108 for detecting incoming calls.
In addition, control signals from the station line loop monitoring circuit (L) 109, hybrid circuit (HYB) 101, codec (CODEC) 102, control signal insertion/extraction circuit (D/I) 103, and insertion/extraction circuit 103 A control device (CPU) 104 extracts the information and controls the trunk circuit, a distribution circuit (SD) 106 distributes control signals to each circuit, a scanning circuit (SCN) 107 obtains status signals from each circuit, and a memory ( MM) 105 mag. The exchange control itself is controlled by the exchange switch (NW) under the central control unit (CC) 112 and memory (MM) 113.
It is controlled by the drive of 111. Control signals are exchanged with the control device 104 of each trunk circuit 100 etc. by the insertion/extraction circuit 103 via the exchange switch 111 using a predetermined time slot.

Therefore, in the present invention, the control device 104 directly samples and detects the signal level obtained by changing the voltage of the calling signal from the office line in the calling signal detection circuit 108.

FIG. 2 is a block diagram of a calling signal detection circuit according to the present invention. In the same figure, the difference from the conventional circuit shown in FIG. 14 is that the integrating circuit consisting of the resistor R and capacitor C shown in _FIG . (Photocoupler) The output B after detecting each positive potential and negative potential of P ₂ and converting the voltage level is directly scanned by the scanning circuit 10.
The problem lies in the fact that it is moving towards 7.

FIG. 3 shows waveform diagrams at various positions for explaining the operation of the circuit of FIG. 2.

In FIG. 2, when a low frequency calling signal with one period of 64 msec, for example, as shown in FIG. 3A, is sent from the office line MW, switch B and capacitor C ₀
A photocoupler is used as an example of a voltage detection element through
This signal is applied to P ₁ and P ₂ . When the calling signal is at a positive potential, the light emitting element LE ₁ of the photocoupler P ₁ emits light except for the non-sensing portion, and as a result the light receiving element LR ₁ becomes conductive, so the output B of the photocoupler P ₁ becomes 0V. Even when the calling signal is at a negative potential, the light emitting element LE ₂ of the photocoupler P ₂ emits light except for the non-sensing portion, and as a result the light receiving element LR ₂ becomes conductive, so the output B of the photocoupler P ₂ becomes 0V. Note that the photocouplers P ₁ and P ₂ are connected in parallel. Both the light receiving elements LE ₁ and LE ₂ are cut off at the non-sensing portions of the photo couplers P ₁ and P ₂ , and the output B of the photo couplers is 5V.

Therefore, this signal level change is converted into a logical value of 1/0 via the scanning circuit 107, and the control device 104 reads the signal level at a predetermined period as shown in FIG. 3C' (arrow).

That is, in the example shown in Fig. 3, 8 msec of the 32 msec half cycle of the calling signal A is a non-sensing part, and 24 msec.
The seconds are the most moving part. That is, when the calling signal A is received, the output B of the photocoupler is
3/4 is 0V and 1/4 is 5V. The present invention focuses on this point and samples the output B of the photocoupler via the scanning circuit 107 at least three times at equal time intervals. FIG. 3 shows an example in which sampling is performed using a clock signal CLK at 8 msec intervals. In the scanning circuit 107, the clock signal
The voltage +5V or 0V of the output B of the photocouplers P ₁ and P ₂ at the time of CLK input is scanned as, for example, logic "1" and logic "0", respectively.

FIG. 4 shows a control circuit as an embodiment of a control device for determining incoming call detection according to the present invention.

When the control device 104 (see FIG. 1) reads the output signal B of the calling signal detection circuit _R1 shown in FIG. 2 via the scanning circuit 107, the input signal C'' is stored in the input register 41 and (for example, the value “0” is stored) and the value of 48 and the comparator 4
7, and if they match, the adder 42 adds them to the count register 43 (the initial value is reset to "0"). This is done by periodically sampling as explained in FIG. 3, for example at a period of 8 ms.

In addition, at a cycle that defines a certain period, for example, 32m
Every s, a comparator 45 compares whether or not the previous value of the count register 43 exceeds the contents of the register 44 storing a predetermined value (threshold value), and if it exceeds the predetermined value, a value of 0/1, for example, is sent to the output register 46. Output as information. After the comparison, the count register 43 is reset. If it is within the predetermined value, simply reset the count register 43 to "0",
The next cycle will be processed.

FIGS. 5 and 6 are time charts showing the process of determining the presence or absence of the call signal and detection, and show examples of when the process of comparing the call signal and a predetermined value are synchronized and when they are asynchronous.

First, in FIG. 5, the level-converted signal C'' of the calling signal is sampled sequentially as shown by the arrow as time passes. If the value changes to "0", it is determined that there is a calling signal and the count register 43 (1, 2...).On the other hand, the value of the count register 43 is checked at the period indicated by the arrow marked with a circle (vertical broken line), and the count register 43 is reset each time. When the value of the count register 43 exceeds a predetermined value, "1" is stored in the output register 46, and if it is within the predetermined value, "0" is stored.

Even if the check cycle of the count register 43 shown in FIG. 6 does not match the cycle of the call signal, the call signal can be detected in the same manner.

7 and 8 are flow charts showing incoming call detection control in the control circuit of FIG. 4.

FIG. 7 shows a process of sampling and counting the call signal at short intervals. When the process is started, the value of the input register is read (1), compared with a predetermined value level (2), If they match, add the value of the count register according to the value of the input register (for example, +
1) and update and store the count register (3).

On the other hand, in the predetermined value (number of times) detection process shown in FIG.
When the value is greater than or equal to the predetermined value, “1” is written to the output register.
is stored (13), and if it is within a predetermined value, "0" is stored in the output register (14), and the count register is initialized (S).

In the above example, the control device counts the number of times a predetermined level signal is detected, and determines that an incoming call has been detected when a predetermined level signal is detected a certain number of times. However, a majority circuit that makes a similar judgment is included in the paging signal detection circuit. It is also possible to provide a system and output the results to the control device.

A second embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 9 is a circuit diagram showing a calling signal detection circuit according to a second embodiment of the present invention. In the same figure, the difference from the conventional circuit in FIG. 15 is that the resistor R in FIG.
and a resistor REG and a majority circuit MDC are provided in place of the capacitor C.

FIG. 10 is a waveform diagram for explaining the operation of the circuit of FIG. 9.

In FIG. 9, when a low frequency calling signal of 64 msec is sent from the central office line MW, for example, as shown in FIG. 10A in one cycle, switch B and capacitor C ₀
This signal is applied to photocouplers P ₁ and P ₂ via. When the calling signal is at a positive potential, the light emitting element LE ₁ of the photocoupler P ₁ emits light except for the non-sensing portion, and as a result the light receiving element LR ₁ becomes conductive, so the output B of the photocoupler P ₁ becomes 0V. Even when the calling signal is at a negative potential, the light emitting element LE ₂ of the photocoupler P ₂ emits light, except for the non-sensing part, and the light receiving element LR ₂ becomes conductive, so the photocoupler
Output B of _P2 becomes 0V. In addition, photocoupler P ₁ ,
P ₂ are connected in parallel. Photocoupler P ₁ , P ₂
In the non-sensing part, both light receiving elements LE ₁ and LE ₂ are cut off, and the output B of the photocoupler is 5V.

In the example shown in FIG. 10, the half cycle of the calling signal A is
Of the 32 msec, 8 msec is the unimpressive part, and 24 msec is the moving part. In other words, when the calling signal A is received, the output B of the photocoupler is 3/3
4 is 0V and 1/4 is 5V. The present invention focuses on this point, and the output B of the photocoupler is
Sample at least three times at equal time intervals by REG. FIG. 10 shows an example in which sampling is performed using a clock signal CLK at intervals of 8 msec. Register REG has a clock signal.
The voltage +5V or 0V of the output B of photocouplers P ₁ and P ₂ at the time of CLK input is stored as, for example, logic "1" and logic "0", respectively. majority circuit
MDC takes n outputs of register REG,
Compare the numbers of logic "1" and logic "0".
If the number of logic "0"s is greater than the number of logic "1"s, the majority circuit MDC outputs an incoming call detection signal to the output OUT. In this case, for the call signal shown in FIG. 10, 3/4 will be stored in the register REG as logic "0" and 1/4 as logic "1". Therefore, in the majority circuit MDC, 3/4 of all input signals are logic “0”
It is only necessary to output an incoming call detection signal when this happens.

FIG. 11 is a circuit diagram showing an example of the configuration of the register REG and majority circuit MDC shown in FIG. 9.
In FIG. 11, the register REG includes four flip-flops FF ₁ to FF ₄ connected in series, and a clock signal CLK is commonly input to the clock input terminal C of each flip-flop. Majority circuit MDC
has four AND gates A ₁ to _{A 4} and one OR gate OR. AND gate _A1 receives the outputs of flip-flops _FF2 , _FF3 , and _FF4 . AND gate A ₂ is flip-flop FF ₁ , FF ₃ ,
Receives the output of FF ₄ . AND gate _A3 receives the outputs of flip-flops _FF1 , _FF2 , and _FF3 .
AND gate A ₄ is flip-flop FF ₁ , FF ₂ ,
Receives the output of FF ₄ .

The output B of the photocoupler is input to the register REG via the inverter INV, and is sequentially shifted every time one bit is input. When the 4 bits are input, if the output of any one of the AND gates _A1 to _A3 becomes logic "1", the input signal B
3 out of 4 bits are logic "0" and a ringing signal can be detected. Therefore, the control device can detect an incoming call simply by detecting this output signal.

FIG. 12 is a block diagram showing an example of a private branch exchange to which the calling signal detection circuit according to the present invention is applied. In the figure, a private branch exchange PBX connected to a central office CO is provided with a plurality of office line trunk packages A to N, and each office line trunk package is provided with a plurality of office line trunks TK ₀ to TK ₃ . Each office line trunk TK ₀ to _{TK 3} is controlled by one control device CPU, each package A to N has the same type of configuration, and is connected to the exchange switch NW by a multiplexing ratio/dispersion device MPX/DMPX. In the present invention, since there is no longer a large capacity capacitor in the ring signal detection circuit _R1 , it is possible to mount a plurality of office line trunks in one package as shown in the figure. A plurality of central office line trunk packages are commonly managed by one central processing unit CPU.

Although the above example has been described as an example applied to a switching system, it can also be applied to a system in which a terminal device (for example, a facsimile terminal) is directly connected to a central office line and incoming call detection is performed on a calling signal.

FIG. 13 shows an example in which the present invention is applied to this type of terminal. An interface circuit TK' is provided between the peripheral device P of the terminal T and the central office exchange CO, and this interface circuit TK' is provided with a ringing signal detection circuit _R1 according to the present invention, and the control device CPU performs the following operations as shown in FIG. Figure 5,
Control is performed as explained in FIG. The control unit exchanges data with the peripheral device P.
This is done through the transmitter/receiver circuit SR under the control of CNT.

[Effects of the Invention] As explained above, according to the present invention, since the integrating circuit is removed from the calling signal detection circuit,
This eliminates the need for a large-capacity capacitor, reduces the circuit scale of the calling signal detection circuit, and facilitates IC packaging. Further, even if the frequency of the calling signal is changed, there is no need to change the hardware, and there is an advantage that it can be handled flexibly.

Note that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the period of the clock signal for sampling is not limited to 8 msec, but may be any other value, and may be changed as appropriate depending on the time period during which the voltage detection element is not sensitive.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram as an example of a system for explaining the outline of the present invention, and FIG. 2 is a configuration diagram of a first embodiment of a calling signal detection circuit according to the present invention.
3 is a waveform diagram at each position for explaining the operation of the circuit in FIG. 2, FIG. 4 is a control circuit diagram as an embodiment of a control device for determining incoming call detection in the present invention, and FIG. Figure 6 is a time chart showing the process of calling signals and the presence/absence of detection;
8 is a flowchart showing the incoming call detection control of FIG. 4, FIG. 9 is a ring signal detection circuit diagram according to the second embodiment of the present invention, and FIG. 10 explains the circuit operation of FIG. 9. FIG. 11 is a detailed configuration diagram of a part of the circuit shown in FIG. 9, FIG. 12 is a block configuration diagram showing an example in which the present invention is applied to a switch, and FIG.
Figure 14 is a block diagram showing an example in which the present invention is applied to a terminal device, Figure 14 is a diagram of a conventional general switching system, specifically showing the interface circuit according to the invention, and Figure 15 is a diagram of a conventional general switching system. 16 is a diagram showing an example of a conventional calling signal detection circuit, and FIG. 16 is a waveform diagram for explaining the operation of the conventional circuit shown in FIG. 15. 100... central office line trunk (TK), 104... control device (CPU), 108... ringing signal detection circuit (R ₁ ),
R ₁ , R ₂ ...Voltage detection element (photocoupler), REG...
Register, MDC...majority circuit, CLK...clock signal.

Claims (1)

[Scope of Claims] A device for detecting an incoming call based on a calling signal sent from a line, comprising: converting means (r, P ₁ , P ₂ ) for converting the calling signal into a rectangular wave; and the calling signal. A holding means (REG) that samples a rectangular wave obtained by converting the signal at a constant period and outputs all the sampled values within a predetermined time; and a majority vote of the plurality of sampling values output from the holding circuit (REG); majority deciding means (MDC) for determining the proportion of the predetermined signal level within the certain time; and an output signal of the majority deciding means (MDC);
An incoming call detection method characterized by identifying the presence or absence of a calling signal from the line.