JP7567918B2 - Polarity reversing circuit, control device, control method, and control program - Google Patents

Description

The present invention relates to a polarity reversing circuit, a control device, a control method, and a control program.

In addition to landline phones for household use, public telephone services are also common, where coins are inserted into the public phone to allow an unspecified number of people to make calls. Public phone users insert coins into the terminal in advance to cover the cost of the call. The coins inserted are then stored in the terminal in an amount equivalent to the cost of the call, depending on the destination and duration of the call.

At this time, a coin storage signal is sent from the switchboard to the terminal every fixed time (for example, 56 seconds) to inform it of the timing to store inserted coins such as 10 yen coins in the terminal. Because public telephone terminals run on analog circuits, the terminal is made to understand the coin storage signal through a special control that reverses (reverses) the polarity of the current supplied to the terminal for about 2 seconds during a call.

FIG. 13 is a graph of the coin deposit signal.
The coin reception signal (communication reception signal) is expressed as a series of current change patterns passing through periods T1, T2, T3, T4, and T5 in that order. When it is time to transmit the coin reception signal in period T1, the current in the normal state during a call turns off in period T2, and reverses to the reverse state in period T3. It then turns off in period T4, and returns to the normal state in period T5, completing one transmission of the coin reception signal.

FIG. 14 is a diagram showing the configuration of a conventional subscriber telephone system 100Z.
In the subscriber telephone system 100Z, a subscriber circuit 92 accommodated in a telephone exchange at a telephone station and a public telephone terminal 91 installed in a hotel or the like are connected by a subscriber cable.
During period T1 in Fig. 13, the subscriber circuit 92 is in a forward normal state by passing a current through terminal 92X, terminal 91, and terminal 92Y in that order. On the other hand, during period T3 in Fig. 13, the subscriber circuit 92 is in a reverse state by passing a current through terminal 92Y, terminal 91, and terminal 92X in that order.

The subscriber circuit 92 is equipped with the following seven functions. These seven functions are collectively called "BORSCHT" functions, which is an abbreviation of the first letters of the alphabet.
・Battery feed
・Over voltage protection
・Ringing (call signal transmission function)
・Supervision (monitoring function)
・Coder/decoder (encoding/decoding function)
・Hybrid (2-wire to 4-wire conversion function)
- Testing (Subscriber line test function)

Returning to FIG. 13, at each division of periods such as between periods T1 and T2, the change in current was steep (vertical graph line), so the polarity inversion caused noise that was unpleasant for users during calls.
Therefore, Patent Document 1 describes an invention for enhancing the smooth change in current inside a subscriber circuit.

Japanese Unexamined Patent Publication No. 183891/1983

In order to add a polarity reversal function for transmitting signals such as coin receipt to a conventional exchange, it is necessary to prepare dedicated electric and electronic circuits and expand the internal design of the exchange in a complex manner, which is costly. For example, in order to realize the polarity reversal function, it is necessary to accommodate both a first power supply function for supplying a current in a normal state and a second power supply function for supplying a current in a reverse state in the same subscriber circuit.
Furthermore, the subscriber circuit of Patent Document 1 has a complex structure due to the expansion performed to smooth the change in current.

Therefore, the main objective of this invention is to add a polarity reversal function to conventional switching equipment at low cost.

In order to solve the above problems, the polarity changing circuit of the present invention has the following features.
The present invention relates to a polarity reversing circuit for reversing the polarity of a current supplied from a subscriber circuit to a terminal,
a first subscriber line for supplying a current from the subscriber circuit, a second subscriber line for allowing the current supplied from the first subscriber line to flow through the subscriber circuit, and a first terminal line and a second terminal line connected to the terminal,
a normal state in which a current from the first subscriber line is passed through the first terminal line, and a current from the second terminal line after power is supplied to the terminal is passed through the second subscriber line;
an off state in which current from the first subscriber line is cut off to the first terminal line and the second terminal line;
a switch mechanism capable of switching between a reverse state in which a current from the first terminal line is passed through the second terminal line while a current from the first terminal line is passed through the second subscriber line after power is supplied to the terminal;
a first electrical filter circuit for smoothing out changes in the current;
The audio signal passing device further comprises a second electric filter circuit arranged in parallel with the first electric filter circuit, the second electric filter circuit passing an audio signal .

According to the present invention, it is possible to add a polarity reversal function to a conventional switching system at low cost.

FIG. 1 is a configuration diagram of a first subscriber telephone system according to an embodiment of the present invention. 4 is a state transition table of the first subscriber telephone system according to the present embodiment. FIG. 2 is a hardware configuration diagram of a control device according to the present embodiment. FIG. 2 is a configuration diagram of a second subscriber telephone system according to the present embodiment. 11 is a state transition table of the second subscriber telephone system according to the present embodiment. FIG. 11 is a configuration diagram of a third subscriber telephone system according to the present embodiment. 13 is a first example of a state transition table of the third subscriber telephone system according to the present embodiment. 13 is a second example of a state transition table of the third subscriber telephone system according to the present embodiment. FIG. 13 is a configuration diagram of a fourth subscriber telephone system according to the present embodiment. 13 is a state transition table of the fourth subscriber telephone system according to the present embodiment. FIG. 13 is a configuration diagram of a fifth subscriber telephone system according to the present embodiment. 13 is a state transition table of the fifth subscriber telephone system according to the present embodiment. 13 is a graph showing signals such as coin storage. FIG. 1 is a diagram illustrating the configuration of a conventional subscriber telephone system.

Below, one embodiment of the present invention is described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a first subscriber telephone system 100A.
The subscriber telephone system 100A is configured by inserting a polarity inversion circuit 3 between a subscriber circuit 2 of an exchange and a terminal 1 of a public telephone, for inverting the polarity of the current supplied from a subscriber cable to the terminal 1. The subscriber circuit 2 in Fig. 1 is equipped with at least the following three functions among the "BORSCHT" functions mounted on the subscriber circuit 92 in Fig. 14.
・Battery feed
・Coder/decoder (encoding/decoding function)
・Hybrid (2-wire to 4-wire conversion function)

The polarity reversing circuit 3 is connected to the outside via the following four lines.
The first subscriber line connects between terminals 2X and P1.
The second subscriber line connects between terminals 2Y and P4.
The first terminal wire connects between terminal P2 and terminal 1.
A second terminal wire connects between terminal P3 and terminal 1.

The polarity reversing circuit 3 has the following four switches as a switch mechanism for realizing the polarity reversing function. This polarity reversing function is a new function that is not included in the conventional "BORSCHT" function.
Switch Sn1 that turns the connection between terminals P1 and P2 on and off
・Switch Sr1 that turns the connection between terminals P1 and P3 on and off
Switch Sr2 that turns the connection between terminals P2 and P4 on and off
Switch Sn2 that turns the connection between terminals P3 and P4 on and off
The symbols for these switches are a combination of "S" which indicates the switch, "n or r" which indicates that it is turned on when in the normal state (n) or reversed state (r), and "1 or 2" which indicates whether it is the first or second from the top. For example, to switch to the normal state, the two switches Sn1 and Sn2 are turned on.

The power supply function of the subscriber circuit 2 always keeps current flowing in the same direction (terminal 2X → polarity-reversing circuit 3 → terminal 2Y). By combining the on and off switches of the polarity-reversing circuit 3, it is possible to realize both a normal state in which current flows in the forward direction to the terminal 1, and a reverse state in which current flows in the reverse direction to the terminal 1 (see FIG. 2 for details).
The subscriber telephone system 100A also has a control device 4 for transmitting control signals to each switch of the polarity reversing circuit 3 to control its on/off state. The control device 4, in cooperation with the subscriber circuit 2, switches each switch of the polarity reversing circuit 3 so that a coin reception signal can be transmitted at a predetermined timing, such as every 10 yen coin, every fixed time (for example, every 56 seconds).
In addition, the coin storage signal etc. that the control device 4 instructs using the polarity reversing function of the polarity reversing circuit 3 can be applied to a "response storage signal" and a "100 yen storage signal" in addition to the communication storage signal of Figure 13.

2 is a state transition table of the first subscriber telephone system 100 A. This table associates the on/off states of the switches Sn1 and Sn2 with the on/off states of the switches Sr1 and Sr2 and the state of current flow for each of the periods T1 to T5 shown in FIG.
In the normal state of periods T1 and T5, the control device 4 turns on (closes) the switches Sn1 and Sn2 and turns off (opens) the switches Sr1 and Sr2. As a result, the current supplied from the terminal 2X of the subscriber circuit 2 passes through the terminals 2X → P1 → P2 → terminal 1 → P3 → P4 → 2Y in this order, so that a constant current flows in the forward direction.

In the OFF state of periods T2 and T4, the control device 4 turns off all four switches Sn1, Sn2, Sr1, and Sr2, thereby cutting off all connections between the subscriber circuit 2 and the terminal 1 and bringing them into the OFF state.
In the reverse state of period T3, the control device 4 turns off the switches Sn1 and Sn2 and turns on the switches Sr1 and Sr2. As a result, the current supplied from the terminal 2X of the subscriber circuit 2 passes through the terminals 2X → P1 → P3 → terminal 1 → P2 → P4 → 2Y in this order, so that a constant current flows in the reverse direction.

FIG. 3 is a diagram showing the hardware configuration of the control device 4.
The control device 4 is configured as a computer 900 having a CPU 901 , a RAM 902 , a ROM 903 , a HDD 904 , a communication I/F 905 , an input/output I/F 906 , and a media I/F 907 .
The communication I/F 905 is connected to an external communication device 915. The input/output I/F 906 is connected to an input/output device 916. The media I/F 907 reads and writes data from a recording medium 917. Furthermore, the CPU 901 controls each processing unit by executing a program (also called an application or its abbreviation, "app") loaded into the RAM 902. This program can be distributed via a communication line, or can be recorded on a recording medium 917 such as a CD-ROM and distributed.

FIG. 4 is a diagram showing the configuration of the second subscriber telephone system 100B.
In addition to the configuration of the subscriber telephone system 100A in FIG. 1, this subscriber telephone system 100B further includes, within the polarity-reversing circuit 3, coils L1 and L2, for example, as a first electric filter circuit provided for the purpose of smoothing out changes in current.
As a result, even if the current changes abruptly at the time of polarity inversion, such as at the boundary between periods T1 and T2, the current can pass through coils L1 and L2 to smooth the change in current, thereby suppressing noise that would otherwise occur if the current change was abrupt.

FIG. 5 is a state transition table for the second subscriber telephone system 100B.
The on/off combinations of the switches in each period in the state transition table are the same in Fig. 5 and Fig. 2. However, the difference is that in the state transition table in Fig. 5, the change in current in each period is smoother.
For example, the current shifts from normal to off instantaneously (rapidly) from the end of period T1 to the start of period T2 in Fig. 13. On the other hand, in the second subscriber telephone system 100B, the current is slightly weaker at the start of period T2 than at the end of period T1, and gradually weakens in the first half of period T2 so that the current is turned off in the second half of period T2 (see the waveform in Fig. 3(f) of Patent Document 1).

FIG. 6 is a diagram showing the configuration of a third subscriber telephone system 100C.
In addition to the configuration of the subscriber telephone system 100B in Fig. 4, this subscriber telephone system 100C adds a first nullifying circuit for nullifying the first electric filter circuit (coils L1, L2) in the polarity reversing circuit 3. The first nullifying circuit is composed of, for example, a switch SL1 parallel to the coil L1 and a switch SL2 parallel to the coil L2.
As a result, when a signal affected by the first electric filter circuit (coils L1, L2) (hereinafter referred to as the affected signal) is transmitted from the subscriber circuit 2 to the terminal 1, the influence of the first electric filter circuit can be appropriately eliminated by bypassing the first electric filter circuit via switches SL1, SL2.

FIG. 7 is a first example of a state transition table for the third subscriber telephone system 100C.
In the first example, since no influence signal flows, the control device 4 turns off the switches SL1 and SL2 for the entire period T1 to T5 during polarity inversion. As a result, a current flows through the first electric filter circuit (coils L1 and L2), and the current state in each period is the same in Figure 7 and Figure 5. Therefore, the subscriber telephone system 100C, like the subscriber telephone system 100B, can suppress noise that occurs when the current changes sharply.

FIG. 8 is a second example of a state transition table for the third subscriber telephone system 100C.
In the second example, since an influence signal flows, the control device 4 turns on the switches SL1 and SL2 for the entire period T1 to T5 during polarity inversion. As a result, no current flows through the first electric filter circuit (coils L1 and L2), and the current state during each period is the same in Figure 8 and Figure 2. Therefore, the subscriber telephone system 100C can transmit a coin reception signal in the same way as the subscriber telephone system 100A.

FIG. 9 is a diagram showing the configuration of a fourth subscriber telephone system 100D.
In addition to the configuration of the subscriber telephone system 100B in Fig. 4, this subscriber telephone system 100D adds a second electric filter circuit that passes voice signals in parallel with the first electric filter circuit (coils L1, L2) to the polarity commutation circuit 3. The second electric filter circuit is composed of, for example, a capacitor C1 in parallel with the coil L1 and a capacitor C2 in parallel with the coil L2.

As a result, even if the first electrical filter circuit (coils L1, L2) increases the electrical impedance for high-frequency audio signals (such as voice, fax signals, and modem signals) and attenuates the high-frequency audio signals, the audio signals can pass through the polarity reversal circuit 3. This makes it possible to appropriately prevent situations in which voice becomes difficult to hear, or in which communication becomes impossible due to attenuation of fax and modem signals.

FIG. 10 is a state transition table for the fourth subscriber telephone system 100D.
The state transition table in Fig. 10 has the same first row (Sn1, Sn2) to third row (current) as the state transition table in Fig. 5. On the other hand, the state transition table in Fig. 10 newly includes a fourth row (row indicating the quality of the audio signal), which indicates a state in which, during the period T2 to T5, noise is heard momentarily in the audio signal, but the attenuation of the audio signal is suppressed by capacitors C1 and C2, so that the audio can be heard.

FIG. 11 is a diagram showing the configuration of a fifth subscriber telephone system 100E.
In addition to the configuration of the subscriber telephone system 100D in Fig. 9, this subscriber telephone system 100E adds a second nullifying circuit for enabling (activating) or disabling a second electric filter circuit (capacitors C1, C2) that passes voice signals to the polarity inverting circuit 3. The second nullifying circuit is composed of, for example, a switch SC1 in series with the capacitor C1 and a switch SC2 in series with the capacitor C2.
This allows noise generated during polarity reversal to be blocked so that it cannot be heard by the user during a call. Note that when polarity reversal occurs, a potential difference occurs across the coils L1 and L2, and a potential difference also occurs across the capacitors C1 and C2, which generates noise.

Fig. 12 is a state transition table of the fifth subscriber telephone system 100E. When the state transition table of Fig. 12 is compared with the state transition table of Fig. 10, the following lines are the same.
First row of FIG. 10 and first row of FIG. 12 (on/off states of switches Sn1 and Sn2)
10, line 2 and 12, line 3 (on/off states of switches Sr1 and Sr2)
- The third row in FIG. 10 and the fifth row in FIG. 12 (current state)

The states of the switches SC1 and SC2 in each period of FIG. 12 will now be described.
In the normal state of period T1, the control device 4 turns on the switches SC1 and SC2. As a result, sound can be heard, similar to period T1 in Fig. 10. In the off state of periods T2 and T4, the control device 4 turns off the switches SC1 and SC2. As a result, sound cannot be heard for a short period of time.
In the reverse state of period T3, the control device 4 turns off the switches SC1 and SC2, and turns on the switches SC1 and SC2 with a delay from turning on the switches Sr1 and Sr2 (for example, after there is no potential difference between both ends of the coils L1 and L2). As a result, the audio signal becomes audible with a delay from turning on the switches Sr1 and Sr2.

In the normal state during period T5, the control device 4 turns on the switches SC1 and SC2 with a delay from turning on the switches Sn1 and Sn2 (for example, after there is no potential difference between both ends of the coils L1 and L2). This allows the audio signal to be heard with a delay from turning on the switches Sn1 and Sn2.
As described above with reference to FIG. 12, the control device 4 prevents the generation of noise by minutely controlling the period during which the second electric filter circuit (capacitors C1, C2) that passes the audio signal is enabled.
Furthermore, the subscriber circuits 2 and the polarity inversion circuits 3 of the subscriber telephone systems 100A to 100E may be configured as separate housings, or may be accommodated in the same housing (switchboard).

[effect]
The present invention relates to a polarity inversion circuit 3 for inverting the polarity of a current supplied from a subscriber circuit 2 to a terminal 1,
a first subscriber line for supplying a current from the subscriber circuit 2, a second subscriber line for allowing the current supplied from the first subscriber line to flow through the subscriber circuit 2, and a first terminal line and a second terminal line connected to the terminal 1,
a normal state in which a current from the first subscriber line is passed through the first terminal line while a current from the second terminal line after power is supplied to the terminal 1 is passed through the second subscriber line;
an off state in which current from the first subscriber line is cut off to the first terminal line and the second terminal line;
The present invention is characterized by having a switch mechanism (switches Sn1, Sn2, Sr1, Sr2) that can switch between a first state in which a current from the first subscriber line is passed to the second terminal line while a second state in which a current from the first terminal line after powering the terminal 1 is passed to the second subscriber line.
The present invention also relates to a control device 4 for controlling the switch mechanism of the polarity reversing circuit 3.

This allows the use of subscriber circuit 2, which does not take into consideration the function of reversing the polarity of the current supplied to terminal 1, and adds polarity reversal circuit 3 to its exterior, eliminating the need to design the entire switchboard from scratch. This reduces the design costs of the switchboard for transmitting the "coin deposit signal," and ultimately reduces the equipment costs of the telephone base station in which the switchboard is installed.

The present invention is characterized in that the polarity commutating circuit 3 further comprises a first electrical filter circuit (coils L1, L2) for smoothing out changes in current.
This makes it possible to suppress noise that occurs when the current changes suddenly, at low cost, without using a dedicated exchange equipped with an extension that smooths out the current changes, as in Patent Document 1.

The present invention is characterized in that the polarity commutating circuit 3 further includes a first disabling circuit (switches SL1, SL2) for disabling the first electric filter circuit, located in parallel with the first electric filter circuit.
This allows only signals that are affected by the first electric filter circuit to bypass the first electric filter circuit.

The present invention is characterized in that the polarity commutating circuit 3 further comprises a second electric filter circuit (capacitors C1, C2) for passing audio signals, located in parallel with the first electric filter circuit.
As a result, even if a high-frequency audio signal is attenuated when passing through the first electric filter circuit, the attenuation of the audio signal can be suppressed via the second electric filter circuit.

The present invention is characterized in that the polarity commutating circuit 3 further includes a second disabling circuit (switches SC1, SC2) for disabling the second electric filter circuit, at a location in series with the second electric filter circuit.
This makes it possible to suppress noise that is generated due to a potential difference occurring across the second electric filter circuit.

Reference Signs List 1 Terminal 2 Subscriber circuit 3 Inverting circuit 4 Control device 100 Subscriber telephone system C1, C2 Capacitor (second electric filter circuit)
L1, L2 Coil (first electric filter circuit)
SC1, SC2 Switch (second invalidation circuit)
SL1, SL2 Switch (first nullification circuit)
Sn1, Sn2, Sr1, Sr2 Switch (switch mechanism)

Claims (6)

A polarity reversing circuit that reverses the polarity of a current supplied from a subscriber circuit to a terminal,
a first subscriber line for supplying a current from the subscriber circuit, a second subscriber line for allowing the current supplied from the first subscriber line to flow through the subscriber circuit, and a first terminal line and a second terminal line connected to the terminal,
a normal state in which a current from the first subscriber line is passed through the first terminal line, and a current from the second terminal line after power is supplied to the terminal is passed through the second subscriber line;
an off state in which current from the first subscriber line is cut off to the first terminal line and the second terminal line;
a switch mechanism capable of switching between a reverse state in which a current from the first terminal line is passed through the second terminal line while a current from the first terminal line is passed through the second subscriber line after power is supplied to the terminal;
a first electrical filter circuit for smoothing out changes in the current;
A polarity inversion circuit comprising: a second electric filter circuit arranged in parallel with the first electric filter circuit for passing an audio signal. 2. The polarity commutating circuit according to claim 1, further comprising a first neutralizing circuit disposed in parallel with the first electric filter circuit and configured to neutralize the first electric filter circuit. 2. The polarity commutating circuit according to claim 1, further comprising a second neutralizing circuit disposed in series with the second electric filter circuit for neutralizing the second electric filter circuit. A control device for controlling the polarity changing circuit according to any one of claims 1 to 3 ,
The control device switches between the normal state, the off state, and the reverse state by transmitting a control signal to the switch mechanism. 4. A control method according to claim 1, wherein a control device for controlling the polarity reversing circuit switches between the normal state, the off state, and the reverse state by transmitting a control signal to the switch mechanism. A control program for causing a computer to function as the control device according to claim 4 .

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