JPH09162975A - Call signal transmission circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a call so that pulse-like voltage becoming the cause of noise is prevented from occurring on a subscriber line at the time of switching the control of the ring transmission/silent transmission of a call signal transmission circuit on call signal transmission in the subscriber circuit of a telephone exchange. SOLUTION: The call signal transmission circuit controls call signal transmission/transmission stop to a subscriber line by on/off-controlling a polarity inversion switch 4 and a call signal transmission switch 5 connecting/cutting a call signal source 3 to the subscriber line, which the subscriber circuit possesses. A shift period in prescribed length is provided between a call signal transmission period and a call signal transmission stop period. The subscriber line is set in an open state by off-controlling the polarity inversion switch 4 and the call signal source 3 is detached from the subscriber line by off- controlling the call signal transmission switch 5. Thus, feeding circuits 1 and 2 are off-controlled in the shift period to call signal transmission from call signal transmission stop.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calling signal transmission circuit in a subscriber circuit of a telephone exchange.

[0002]

2. Description of the Related Art The present invention is an improvement of a calling signal sending circuit using a polarity reversing switch as described in, for example, Japanese Patent Publication No. 3-5104, "Calling signal sending system". The present invention is an improvement of the control sequence, and there is no fundamental difference in the circuit configuration between the present invention and the prior art.
The related art will be described with reference to the circuit of the embodiment of the present invention.

In the figure, S1 to S7 are PNPN switches (for example, thyristors), of which S4 to S7 are GTOs.
It has a (gate turn-off) function. BA is a power supply circuit on the A line (power supply side subscriber line) side, BB is a B line (ground side subscriber line) side power supply circuit, CR is a ringing signal source (usually 79 Vrms), and R1 and R2 are Resistance, OR is a logical sum gate, TEL is a subscriber's telephone, VBB is a station power supply (usually-
48V). Switches S1 to S7 and power supply circuit B
A and BB are on / off controlled by control signals (RNG, SLT, GTO, BFA, BFB) sent from a control circuit (not shown).

When a calling signal is sent to the telephone TEL,
The switches S4 and S7 are turned off to alternately perform ring transmission and silent transmission. When sending a ring, control signal R
NG, BFA, and BFB are active, the control signal SLT is inactive, the switches S1 to S3 and S6 and the power supply circuits BA and BB are turned on, and the switch S5 is turned off. Although the ringing signal current flows, the ringing signal current path is the ringing signal voltage VCR.
It changes as follows with the change of. When VCR> VBB: Ringing signal source CR → resistor R1 → switch S1 → telephone TE
L → switch S6 → power supply circuit BB → station power supply VBB when VCR <VBB station power supply VBB → resistor R2 → switch S3 → phone TEL
→ switch S2 → resistor R1 → ringing signal source CR

At the time of silent transmission, the control signals SLT and BF
When A and BFB are active and the control signal RNG is inactive, the switches S5 and S6 and the power supply circuits BA and BB are turned on, and the switches S1 to S3 are turned off. Since the power supply at this time is DC power supply from the local power supply VBB, the telephone TEL
During on-hook, the DC route is cut by the capacitor in the bell circuit, and no current flows through the subscriber line.

Further, the PNPN switch has a self-holding function that once it is turned on and becomes conductive, it is not turned off until the conduction current becomes equal to or less than the holding current even if the on control is stopped. Therefore, in order to turn off the PNPN switch in conduction, it is necessary to stop the on control and then perform natural disconnection to suppress the conduction current to be equal to or less than the holding current or forced disconnection by the GTO circuit.

Since only the alternating current passes through the switches S1 to S3, if the ON control is stopped, the conduction current is naturally cut off when the conduction current becomes less than the holding current. Therefore switch S
1 to S3 are not equipped with the GTO function. On the other hand, the switches S4 to S7 are originally switches for reversing the polarity of the subscriber line, and since a direct current is passing during a call and spontaneous disconnection is impossible, a GTO function is added.

When the ring signal transmission and the silent transmission are alternately performed in the ringing signal transmission circuit of FIG. 2, P is used when the control state is switched.
The following problems may occur due to the self-holding function of the NPN switch.

At the time of switching from ring transmission to silent transmission When the ring signal is switched to silent transmission when the ringing signal voltage VCR is a negative voltage, the conduction current becomes equal to or less than the holding current after the ON control of the switch S2 is stopped. Since it takes a certain period until the switch S2 is disconnected, the switch S5 is turned on before the switch S2 is cut off, and an inrush current flows through a path of ground → feeding circuit BB → switch S5 → switch S2 → resistor R1 → call signal source CR. At this time, the power supply circuit BB in the ON state has a low resistance of about several hundred ohms, so this rush current becomes an excessive current, and the power supply circuit BB is destroyed or overheated.

At the time of switching from silent transmission to ring transmission When the line resistance is small due to insulation deterioration of the subscriber's line, grounding → feeding circuit BB → switch S5 due to leakage current between subscriber lines at silent transmission → switch S6
→ DC loop current of the route of power supply circuit BA → station power supply flows. If this DC loop current is larger than the holding current of the PNPN switch, the switch S5 cannot be disconnected by stopping the ON control. Therefore, when the ring signal transmission is switched from the silent transmission when the ringing signal voltage VCR <the station power supply VBB, the switch S5 remains in the ON state and the switch S2 is turned on. An excessive rush current flows through the route of S5 → switch S2 → resistor R1 → call signal source CR, and the power supply circuit BB is destroyed or overheated.

Conventionally, in order to prevent this inrush current,
By utilizing the GTO function of the switches S4 to S7, the GTO control for a certain period of time was performed when the control state was changed.
That is, the switch S5 is forcibly cut off by activating the control signal GTO to the switches S4 to S7 for a certain period between the ring sending period and the silent sending period. FIG. 7 shows an example of a call control sequence in a call signal transmission circuit of the prior art. In the figure, the ring-to-silent transition period is longer than the silent-> ring transition period because the switch S5 is at least during the ring-to-silent transition period during which the ringing signal voltage VCR is a negative voltage. This is because it is necessary to continue the forced disconnection so as not to be turned on, whereas it is only necessary to turn off the conducting switch S5 once during the transition from silent to ring, and it is not necessary to continue the forced disconnection.

[0012]

Equivalent circuits of the ringing signal sending circuit of FIG. 2 at ring sending and silent sending are shown in FIGS. 8 and 9, respectively. The symbols of the directional switches in these equivalent circuit diagrams correspond to the symbols of the PNPN switch and the feeding circuit in the circuit diagram of FIG. The ring circuit inside the telephone TEL is represented equivalently.

FIG. 10 is an equivalent circuit at the time of transition from ring to silent and at transition from silent to ring. At this time, all of the switches S1 to S7 are turned off, but the switches S4 to S7 are forcibly cut off by the control signal GTO, so that the subscriber line is not opened and the directional switch is used as shown in FIG. Will be connected to ground. The reason will be described below.

FIG. 11 shows a configuration example of a PNPN switch with a GTO circuit. In this example, when the control signal GTO becomes active, a current flows through the path of the transistor Q1 → diode D1 → transistor Q2 of the GTO circuit and P
Since the gate and cathode of the NPN switch are short-circuited, P
The NPN switch is turned off. When the GTO circuit as in this example is provided in the switches S4 to S7 of the ringing signal sending circuit of FIG. 2, the subscriber line is grounded through the GTO circuit of the PNPN switch while the control signal GTO is active. This means that they are connected, and therefore, the connection points between the switches S4 to S7 and the subscriber line are almost at ground potential.

Conventionally, since the subscriber line is connected to the ground through the directional switch at the time of switching the ring transmission / silent transmission as described above, a large amplitude pulsed voltage is periodically generated on the subscriber line. It was FIG. 12 shows an example of voltage waveforms on lines A and B when the call signal transmission circuit of FIG. 2 is controlled by the call control sequence of FIG. Usually, the subscriber line is formed by a bundle of cables for a plurality of lines, and the voltage induced between the cables due to such a large-amplitude pulse crosstalks to other lines, causing noise.

The present invention has been made in view of the above problems, and prevents pulse-like voltage, which causes noise, from occurring on the subscriber line when the ring transmission / silent transmission control is switched in the ringing signal transmission circuit. The purpose is to perform call control.

[0017]

FIG. 1 is an explanatory view of the principle according to the present invention. In order to solve the above-mentioned problem, in the present invention, the ground side power feeding circuit 1 and the power source side power feeding circuit 2
From the semiconductor switches 41 to 44 connected between the ringing signal source 3, the ground side subscriber line 7 and the power source side subscriber line 8, and the ground side feeding circuit 1 and the power source side feeding circuit 2, respectively. The polarity reversing switch 4 and the semiconductor switches 51 and 51 configured to conduct bidirectionally between the ringing signal source 3 and the power supply side subscriber line 8 at the time of ON control, and the power supply 6 to the ground side subscriber at the time of ON control. And a ringing signal sending switch 5 composed of a semiconductor switch 53 configured to conduct in the direction toward the line 7, and controls the ringing signal sending switch 5 to be turned on during a ringing signal sending period during ringing control. In addition, the polarity reversing switch 4 is arranged so that only the ground side subscriber line 7 and the power supply side power supply circuit 2 are electrically connected.
ON / OFF control, and during the ringing signal transmission stop period during the ringing control, the ringing signal transmission switch 5 is turned off and the polarity reversing switch 4 is turned on / off so that the subscriber line has the reverse polarity. In the call signal transmission circuit, a transition period of a predetermined length is provided between the call signal transmission period and the call signal transmission stop period, the call signal transmission switch 5 is turned off during the transition period, and the polarity is inverted. Provided is a paging signal transmitting circuit in a subscriber circuit, which is characterized in that all switches 4 are turned off.

Further, in the present invention, the ground side power supply circuit may be controlled to be turned off during the transition period from the call signal transmission stop period to the call signal transmission period.

Further, in the present invention, the power supply circuit may be controlled to be turned off during the transition period from the call signal transmission stop period to the call signal transmission period.

[0020]

In the ringing signal sending circuit of FIG. 1, when the ringing control is started, the grounding side power feeding circuit 1 and the power source side power feeding circuit 2 are turned on by the respective control signals, and the ringing signal sending period → transition period → ringing signal sending stop period. → Send the ringing signal by repeating the cycle of transition period.

During the calling signal sending period, the semiconductor switch 43 in the polarity reversing switch 4 is turned on by the control signal, the semiconductor switches 41, 42 and 44 are turned off by the control signal, and the calling signal sending switch 5 ( The semiconductor switches 51 to 53) are turned on by the control signal. In this state, a ringing signal current is sent from the ringing signal source 3 to the telephone 9 through the subscriber line, but the ringing signal current is generated when the voltage VCR of the ringing signal source 3 is higher than the voltage VBB of the power source 6. -> Semiconductor switch 51-> power supply side subscriber line 8-> telephone 9-> ground side subscriber line 7-> semiconductor switch 43-> power supply side power supply circuit 2-> power supply 6, and the voltage VCR of the ringing signal source 3 is the power supply. 6 voltage V
When it is lower than BB, it flows through the route of power source 6 → semiconductor switch 53 → ground side subscriber line 7 → telephone 9 → power source side subscriber line 8 → semiconductor switch 52 → call signal source 3.

During the transition period from the ringing signal transmission period to the ringing signal transmission stop period, the polarity inversion switch 4 (semiconductor switches 41 to 44) and the ringing signal transmission switch 5 (semiconductor switches 51 to 53) are controlled by the control signals to. All off. Therefore, during the transition period, the ground side subscriber line 7 and the power source side subscriber line 8 are equivalently opened.

During the call signal transmission stop period, the semiconductor switches 41 and 44 in the polarity reversing switch 4 are turned off by the control signal, and the semiconductor switches 42 and 43 are turned on by the control signal, respectively, so that the subscriber line is opened. In addition to the reverse polarity, the call signal transmission switch 5 is turned off by the control signal. In this state, DC power is supplied to the subscriber line from the power source 6, but no DC current flows through the subscriber line because the DC route is cut by the capacitor of the ring circuit of the telephone 9.

The transition period from the ringing signal transmission suspension period to the ringing signal suspension period is the same as the transition period from the ringing signal transmission period to the ringing signal transmission suspension period.

However, the length of the transition period from the calling signal sending period to the calling signal sending stop period is set to be longer than the period in which the calling signal voltage VCR becomes a negative voltage in one cycle of the calling signal. By providing such a transition period, even when the call signal transmission period ends when the call signal voltage VCR is a negative voltage (that is, when a current is flowing through the semiconductor 52), the conduction current of the semiconductor switch 52 decreases and naturally. Since it is guaranteed that the semiconductor switch 42 is turned on after the disconnection, it is possible to prevent the semiconductor switch 42 and the semiconductor 52 from being turned on at the same time and causing an excessive current to flow in the ground side feeding circuit 1.

Further, during the period when the call signal transmission is stopped due to the insulation deterioration between the subscriber lines, the semiconductor is routed through the path of ground → ground side power supply circuit 1 → semiconductor switch 42 → semiconductor switch 43 → power supply side power supply switch 2 → power supply 6. Even when the semiconductor switch 42 cannot be turned off by the control signal at the end of the ringing signal transmission stop period due to the DC loop current exceeding the switch holding current, during the transition period from the ringing signal transmission stop period to the ringing signal stop period. The ground side power supply circuit 1 is turned off by a control signal, or the power supply side power supply circuit 2
Since the DC loop current flowing through the path is stopped by turning off the control signal by the control signal, the semiconductor switch 42 can be surely turned off. As a result, it is possible to prevent the semiconductor switch 42 and the semiconductor 52 from being turned on at the same time so that an excessive current flows through the ground side power feeding circuit 1.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing an embodiment of a calling signal transmission circuit according to the present invention. The circuit configuration has already been described in the section of the prior art and will not be described here.

FIG. 3 shows a call control sequence in this embodiment. Also in the present invention, a transition period is provided between the ring transmission period and the silent transmission period as in the call control sequence of the conventional technique, but the difference from the conventional technique is that the GTO control of the switches S4 to S7 is performed during the transition period. The point is that only the ON control is stopped. That is, the control signal RNG starts the ring delivery period is from active to inactive, then the control signal R after a time T _R
NG changes from active to inactive, the ring transmission period ends, and after time T _RS , the control signal SLT changes from inactive to active to start the silent transmission period, and after time T _S , the control signal SLT changes from active. The ringing signal is transmitted by repeating the cycle of becoming inactive and ending the silent transmission period, and after time T _SR , the control signal RNG becomes inactive and becomes active to start the ring transmission period. The control signal GTO remains inactive during call control.

In this way, the ring → silent transition period T
_RSAnd silent → ring transition period T _SRControl signal RN
Both G and SLT are inactive, so switch S1
~ S7 are all turned off. Only switch S5 here
Looking at the ring transmission period T_ROff, ring → siren
Transition period T_RSIs off, silent transmission period T_SHa
N, Silent → Ring transition period T_SRIs off
Repeat the cycle.

As shown in FIG. 4, when the period in which the call signal voltage VCR in one cycle of the ringing signal is a negative voltage and T _CL, finished ring delivery period during T _CL switches S
Even if the ON control of 2 is stopped, the switch S2 is not turned off until VCR = 0. Therefore, period T _RS > period T
_{If the} call control is performed so as to be _CL , it is ensured that the switch S5 is turned on after the switch S2 is turned on, so that it is possible to prevent the inrush current at the time of transition from ring to silent.

Further, in the transition from silent to ring, the ON control of the switch S5 is stopped at the end of the silent transmission period, and the switch S2 is ON-controlled at the start of the ring transmission period after a lapse of time T _SR, which is usually the case. no problem. However, as explained in the section of the prior art, if a DC loop current greater than the holding current flows through the switch S5 during the silent transmission period due to deterioration of insulation between subscriber lines, the switch S5 can be turned off at the end of the silent transmission period. No
If the switch S2 is turned on at the start of the ring sending period in that state, an inrush current will be generated. In order to prevent this, in the call control sequence of the present embodiment, silent →
During the ring transition period, the power supply circuit BB is controlled by the control signal BFB.
Is controlled off. As a result, the DC loop current due to the deterioration of the insulation between the subscriber lines does not flow, and the switch S5 can be surely turned off during the transition period T _SR , so that the inrush current at the silent → ring transition can be prevented. The same effect can be obtained by turning off the power feeding circuit BA with the control signal BFA instead of turning off the power feeding circuit BB with the control signal BFB.

FIG. 5 is an equivalent circuit of the circuit of this embodiment at the time of transition from ring to silent and at transition from silent to ring. In this case, the control signal G for the switches S4 to S7
Since TO is inactive, the subscriber line is GT
It is not connected to the ground through the O circuit, and is equivalently in an open state where it is not connected to anything.

FIG. 6 shows an example of voltage waveforms on the lines A and B when the circuit of this embodiment is controlled by the call control sequence of FIG. Since the subscriber line is open during the transition period, both the A line and the B line hold the potential immediately before the transition. For example, if the ring sending period ends when the ringing signal voltage VCR is in a positive phase as shown in FIG. 6, the line A holds the potential at the end of the ring sending period during the ring → silent transition period, and the silent sending is performed. Since there is no discharge path even during the period (see the equivalent circuit of FIG. 9), the potential is kept held until the next ring sending period starts. On the other hand, the line B holds the potential at the end of the ring sending period during the ring → silent transition period, but when the silent sending period starts, the potential is discharged and the potential drops to the local power supply voltage (−48V).

By applying the call control sequence of FIG. 3 as described above, it is possible to prevent the generation of a large amplitude pulse voltage on the subscriber line at the time of transition from ring to silent and at transition from silent to ring.

[0035]

As described above, according to the present invention, the pulse-like voltage fluctuation occurring on the subscriber line when the ringing signal sending circuit performs control switching between ring sending and silent sending is performed. It can be suppressed, and thereby noise can be prevented from being induced in the adjacent line.

Further, according to the present invention, since it is possible to prevent the inrush current from flowing in the subscriber circuit, it is not necessary to consider the protection against the inrush current, and the switch and the power feeding circuit can be downsized.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle according to the present invention.

FIG. 2 is a diagram showing a calling signal transmission circuit as an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a call control sequence of the present invention.

FIG. 4 is a diagram for explaining an operation example of switches S2 and S5 during a transition period from ring transmission to silent transmission.

FIG. 5 is a diagram showing an equivalent circuit of a call signal transmission circuit in a transition period in the call control of the present invention.

FIG. 6 is a diagram showing an example of a voltage waveform on a subscriber line when the call control of the present invention is applied.

FIG. 7 is a diagram showing an example of a conventional call control sequence.

FIG. 8 is a diagram showing an equivalent circuit of a ringing signal sending circuit when sending a ring.

FIG. 9 is a diagram showing an equivalent circuit of a call signal transmission circuit during silent transmission.

FIG. 10 is a diagram showing an equivalent circuit of a call signal transmission circuit in a transition period in call control according to a conventional technique.

FIG. 11 is a diagram showing a configuration example of a PNPN switch with a GTO circuit.

FIG. 12 is a diagram showing an example of a voltage waveform on a subscriber line when the call control of the prior art is applied.

[Explanation of symbols]

 1 ground side feeding circuit 2 power side feeding circuit 3 ringing signal source 4 polarity reversing switch 5 ringing signal sending switch 6 power source 7 ground side subscriber line 8 power source side subscriber line 9 telephone 41-44, 51-53 semiconductor switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 000004237 5-7-1 Shiba, Minato-ku, Tokyo (71) Applicant 000005108 Hitachi, Ltd. 4-6-Kanda Surugadai, Chiyoda-ku, Tokyo (72) ) Inventor Masafusa Sato 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Akira Ishizawa, 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo (72) Inventor Hiroshi Hashimoto 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Hideki Kikui 5-7-1, Shiba, Minato-ku, Tokyo NEC Electricity Company (72) Inventor Ota Shinya 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Hitachi, Ltd., Information & Communication Division

Claims (3)

[Claims] 1. A semiconductor switch connected between a ground side power supply circuit and a power supply side power supply circuit, a calling signal source, and each of the ground side and power supply side subscriber lines and each of the ground side and power supply side power supply circuits. A polarity reversing switch, a semiconductor switch configured to conduct bidirectionally between the ringing signal source and the power supply side subscriber line during ON control, and conduction in the direction from the power supply to the ground side subscriber line during ON control A calling signal sending switch composed of a semiconductor switch configured so as to control the turning on of the calling signal sending switch during the calling signal sending period at the time of calling control, and a ground side subscriber line and a power supply. The polarity reversing switch is controlled to be turned on / off so that only the side power supply circuits are electrically connected, and the ringing signal transmission switch is turned on during the ringing signal transmission suspension period during ringing control. In the call signal sending circuit for controlling the polarity and inverting the polarity inversion switch so that the subscriber line has a reverse polarity, a predetermined length is provided between the call signal sending period and the call signal sending stop period. A call signal sending circuit in a subscriber circuit, characterized in that a shift period is provided, and during the shift period, the call signal sending switch is turned off and all the polarity reversing switches are turned off. 2. The call signal transmission circuit according to claim 1, wherein the ground side power supply circuit is off-controlled during a transition period from the call signal transmission stop period to the call signal transmission period. 3. The call signal transmission circuit according to claim 1, wherein the power supply side power supply circuit is turned off during a transition period from the call signal transmission stop period to the call signal transmission period.