JPH02907B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ring trip circuit, and more particularly to a ring trip circuit in a circuit for transmitting a ringing signal in an electronic exchange.

When the communication path is computerized, such as in a time-division electronic exchange, a ringing signal to the called telephone is sent from the subscriber circuit, and as soon as the called telephone answers, the sending of the ringing signal is stopped.

FIG. 1 is a diagram showing an example of a conventional ring trip circuit in a subscriber circuit of a time division electronic exchange. In FIG. 1, when sending a ringing signal R to the called telephone TEL, the relay RL of the subscriber circuit operates under the control of a signal distribution unit (not shown).
A calling signal R weighted with DC voltage -V is sent to the called telephone set TEL. Further, the level detector LV monitors the voltage drop across the resistor R2 inserted in the calling signal transmission path via the waveform device F. When the called telephone is in a non-responsive state, no direct current flows through the resistor R2, and only the ringing signal current (alternating current) flows. In this case, the alternating current component is attenuated by the wave device F, so the level detector LV does not operate. When the called telephone TEL answers, direct current also flows through resistor R2, so
The level detector LV operates by detecting the DC voltage drop across the resistor R2 via the waveform device F. As a result, the operating relay RL is restored and the sending route of the calling signal R is cut off. Power supply circuit for called telephone TEL
Call current is supplied from the FD, and calls are possible.
The audio signal is transmitted to the time division highway via the 2-wire/4-wire conversion circuit 4W.

As is clear from the above explanation, the conventional ring trip circuit uses a resistor R to respond to the called telephone TEL.
Detected by the DC voltage drop of 2. For this purpose, the input of the level detector is equipped with a waveform F for blocking the calling signal.
Is required. Since the frequency of the calling signal R is extremely low (for example, 16 hertz), the circuit constants constituting the wave generator F are large, and the components are also large. In addition, there is a considerable delay in detecting the DC voltage drop via the waveguide F, and the called telephone that answers
There is a possibility that a call signal may be injected into the TEL.

Further, in recent exchange systems, a variety of services is required, and there is more than one type of paging signal. For example, in a private branch exchange, it is desired to notify a subscriber whether a call is coming from an outside line or an extension line by varying the intermittent period of the calling signal.

Generally, the intermittent ringing signal is controlled by turning on and off a ringer sending relay r1 that connects the ringing signal sending circuit to the subscriber line, and the intermittent period is controlled by changing the on/off time of this relay r1. ing. When such intermittent control of the paging signal is performed by the paging signal sending circuit itself of the subscriber circuit, there are the following problems.

As mentioned above, if multiple types of intermittent periods of the calling signal are required, it is necessary to provide a calling signal sending circuit corresponding to each intermittent period.
Subscriber circuits become larger. Furthermore, if you want to change the type of ringing signal according to the subscriber's wishes,
It is necessary to prepare a subscriber circuit equipped with a paging signal sending circuit for each purpose, which results in a lack of versatility.

On the other hand, if the on/off period of the ringer sending relay is controlled by the SD signal sent from the central control device, multiple types of intermittent periods can be obtained with one type of ringing signal sending circuit. And adjusting the SD signal according to the intermittent period is
This can be done by simply changing the software of the central control unit. Therefore, the method of controlling the intermittent period of the paging signal using the SD signal from the central control unit has the advantage that service can be improved without increasing hardware.

An object of the present invention is to provide such a switching system with a system that does not respond to instantaneous or pseudo off-hook caused by noise during transmission of a calling signal or subscriber's erroneous operation, but only responds to a certain off-hook, and performs ring trips without error. An object of the present invention is to provide a ring trip circuit that can be executed reliably.

The above object is to provide an electronic exchange that performs intermittent control of sending out a ringing signal to a subscriber's telephone using a control signal from a central control unit, comprising: a capacitor installed in series in a path for sending out a ringing signal to the subscriber's telephone; an off-hook detection circuit that monitors the voltage at both ends and detects off-hook of the subscriber's telephone while sending out the ringing signal; and an off-hook detection circuit that is set by the detection output of the off-hook detection circuit and reset by the control signal that indicates that the sending of the ringing signal is interrupted. and a holding circuit, and by the output signal of the holding circuit and the control signal,
This is achieved by controlling the transmission of the calling signal on and off.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing a ring trip circuit in an embodiment of the present invention in a subscriber circuit of a time division electronic exchange, and FIG. 3 is a sequence diagram of various signals in FIG. In FIG. 2, the control signal SD shows logic 1 in the idle state,
When sending a ringing signal R to the called telephone TEL, a control signal SD as shown in FIG. 3b is given from a signal distributor (not shown). The control information SD
indicates logic 0 from time t ₁ to t ₂ , and logic 1 from time t ₂ to t _3. The period of logic 0 of this SD signal is as follows.
A paging signal is sent, and the paging signal is interrupted during the logic 1 period. Therefore, intermittent control of the sending of the calling signal is possible by commands from the central control device.
Such control information SD is inverted by gate G1 as shown in FIG. 3c, and sent to gates G3 and G4.
is input. In the vacant state, Foto Capra PH
is not operating, the potential +V1 is applied to the gate G2.
(Logic 1, FIG. 3f) is input, gate G2 is in the conducting state and gate G3 is in the blocking state.
The output of gate G3 is therefore in a logic 1 state as shown in FIG. 3d, keeping gate G4 conductive. Therefore, the output of the gate G1 is inverted by the gate G4 as shown in FIG. 3e and inputted to the driver DV. The driver DV drives the relay RL at time _t1 , as shown in FIG. 3g. When relay RL operates, a ringing signal R is sent to called telephone TEL via capacitor C and resistors R1 and R2 in FIG. In parallel with the capacitor C,
A current detection circuit composed of a photo coupler PH, a constant voltage diode D, and a resistor R4, and a high resistor R3 as a discharge circuit for the capacitor C are connected. Currently, the called telephone TEL is in a non-responsive state, so the DC voltage superimposed on the ringing signal R -
No direct current flows from V. Also, if the voltage drop across the capacitor C due to the call signal R is maintained sufficiently low compared to the breakdown voltage of the constant voltage diode D,
The photo coupler PH in the current detection circuit does not operate. In this manner, from time _t1 to time _t2 , if the called telephone TEL does not respond, the ringing signal R continues to be transmitted during this time as shown in FIG. 3h. From time _t2 to time _t3 , the control information SD becomes logic 1, the relay RL is restored, and the calling signal R is not sent out.
At time _t3 , the control information SD becomes logic 0 again, the relay RL is activated and a ringing signal is sent to the called telephone TEL. When the called telephone TEL responds at time t _H while the ringing signal R is being sent (Fig. 3a), the impedance of the telephone TEL becomes low, and a DC voltage -V is applied between the terminals of the capacitor C, and the voltage of the constant voltage diode D increases. Since the breakdown voltage is exceeded, a pulsating current in which a DC current is superimposed on the ringing signal current flows via the resistor R4. When the voltage drop across resistor R4 due to the pulsating current exceeds the forward voltage of photo coupler PH,
A portion of the pulsating flow begins to flow into the photo coupler PH. As a result, when the photo coupler PH operates,
The potential +V1 (logic 1) input to the gate G2 changes to the ground potential (logic 0) as shown in FIG. 3f. Therefore, the gate G2 is inverted and maintained in the blocked state, and the gate G3 is inverted and maintained in the conductive state. As a result, the output of gate G3 becomes a logic 0 as shown in FIG. 3d, placing gate G4 in a blocking state. The control information SD (FIG. 3b) is therefore no longer input to the driver DV (FIG. 3e) and the relay RL is restored (FIG. 3g). If relay RL is restored, ring signal R
The transmission route is cut off, and the called telephone TEL receives the communication current from the power supply circuit FD. Note that once the output of gate G3 becomes logic 0, the control signal SD
It maintains a logic 0 state regardless of the output of the photo coupler PH until it becomes a logic 1.

The relay off of the SD signal, that is, the instruction signal (logic 1) for the ringing signal disconnection period functions as a reset signal for the holding circuit, and is therefore very effective under the following circumstances.

For example, if a subscriber fails to pick up the phone in a hurry and goes off-hook for a while and then goes off-hook again, the subscriber usually
Wait for the next ringing signal, then pick up the receiver again.

In such a case, since off-hook has been detected once, the transmission of the ringing signal is stopped by this off-hook detection signal, and normally the ringing signal is not transmitted again. however,
According to the configuration of the above embodiment, the holding circuit is reset by the SD signal of logic 1 instructing the disconnection period. Therefore, unless an off-hook detection signal (voltage drop due to resistor R5) is sent out intermittently, the holding circuit is not set by the off-hook detection signal after the above-mentioned reset, and gate G4 is opened. Therefore, the SD signal from the central controller is valid. That is, once the off-hook detection causes the transmission of the paging signal to be stopped immediately, it is possible to continue transmitting the paging signal again depending on the condition of the subscriber thereafter.

Therefore, even if the subscriber accidentally fails to pick up the telephone receiver, the transmission of the ringing signal will not be stopped.

In the configuration of the above embodiment, the sending of the calling signal is completely stopped only when the SD signal intermittently becomes a signal indicating relay off (logic 1). In other words, in this embodiment, the off-hook detection signal is used only when the calling signal is sent (the period following the interruption period).
It is only a signal that controls the stop of sending out a calling signal.

Further, the instantaneous, pseudo-off-hook state described above may be caused by noise on the subscriber line.

As is clear from the above description, according to this embodiment, when the called telephone TEL is not responding, the ringing signal R is sent out via the capacitor C, and the current detection circuit is not operated by the constant voltage diode D. When the called telephone TEL responds, the photo coupler PH of the current detection circuit detects the direct current superimposed on the ringing signal R, and the detection output is held by the gates G2 and G3, and at the same time, the operation of the relay RL is controlled by the control information SD. This prevents the calling signal R from being sent out. Therefore, even if the current flowing through the photo coupler PH is a pulsating current, it is immediately detected and held, so there is no need for a conventional wave generator, and the ring trip is quickly performed.

Note that FIGS. 2 and 3 are only one embodiment of the present invention; for example, the control information SD sent from the signal distribution section is not limited to the format shown in FIG. It is also possible to consider the case where the control information SD for the data is transferred serially and periodically (FIG. 3i). In such a case, as shown in FIG. 4, the control information SD (FIG. 3i) is sent to the gate G1'.
By inputting the clock CLK (FIG. 3j) synchronized with the clock CLK (j in FIG. 3), the effects of the present invention are not impaired. Furthermore, the calling signal R is not limited to one in which the DC voltage -V is superimposed, and even when using a calling signal R in which the earth voltage is superimposed, the present invention can be applied by reversing the connection direction of the photo coupler PH. The effect of is unchanged.

As described above, according to the present invention, it is possible to reliably execute a ring trip by responding only to a certain off-hook without responding to momentary or pseudo off-hook caused by noise during sending of a ringing signal or an erroneous operation by the subscriber. be.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional ring trip circuit in a subscriber circuit of a time division electronic exchange.
2 is a diagram showing a ring trip circuit according to an embodiment of the present invention, FIG. 3 is a sequence diagram of various signals in FIG. 2, and FIG. 4 is a diagram showing a partial modification of FIG. 2. In the figure, TEL is the called telephone, FD is the power supply circuit, 4W is the 2-wire 4-wire conversion circuit, R is the ringing signal, -
V is DC voltage, F is wave detector, LV is level detector,
DV is driver, RL is relay, SD is control information,
G1, G2, G3 and G4 are gates, D is a constant voltage diode, PH is a photo coupler, R1, R
2, R3, R4 and R5 represent resistance.

Claims (1)

[Scope of Claims] 1. In an electronic exchange that performs intermittent control of sending out a calling signal to a subscriber telephone using a control signal from a central control unit, a capacitor provided in series in a calling signal sending path to the subscriber telephone; an off-hook detection circuit that monitors the voltage across the capacitor to detect off-hook of the subscriber's telephone during the sending of the ringing signal; and a control that is set by the detection output of the off-hook detection circuit and indicates that the sending of the ringing signal is interrupted. and a holding circuit that is reset by a signal, and by the output signal of the holding circuit and the control signal,
A ring trip circuit characterized by performing intermittent control of sending out a calling signal.