JPH0232837B2 - KANYUSHAKAIRO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a subscriber circuit that supplies call current to a public telephone, transmits call signals, and sends billing pulses for storing coins.

(Background Art) Figure 1 shows an example of the configuration of a conventional subscriber circuit.
Tel is a public telephone, SLIC is a subscriber circuit, LN1,
LN2 is a communication line, BN (N) is a current supply circuit for normal power supply, BS (R) is a current supply circuit for reverse power supply, BN, BR are power supply control terminals, HYB is 2-wire 4
In the line conversion circuit, FIL is a charging filter, L is an inductance, C is a capacitor, and S1 and S2 are switches.

Figure 2 shows an example of the configuration of a current supply circuit, with OPA,
OPB is an operational amplifier, DC is a direct current feedback circuit, HYB
is a 2-wire 4-wire conversion circuit, Σ is an addition circuit, TRA,
TRB is a power supply transistor, REA, REB are resistors, D1, D2 are diodes to prevent reverse bias of the power supply transistor, SO is a power supply control switch, BF
represents a control terminal, and A and B represent output terminals. In the following description, it is assumed that the control terminal BF controls the power supply control switch so that power is supplied when the control terminal BF is at the H level and that the power supply is stopped when the control terminal BF is at the L level.

FIG. 3 is a diagram explaining the operation of FIG. 1,
WBN is the power supply control signal waveform of the current supply circuit BS (N) for normal power supply, WBR is the power supply control signal waveform of the current supply circuit BS (R) for reverse power supply, and WBS
(N) and WBS(R) represent the operating states of both current supply circuits, WVCD represents the billing filter input waveform, and WVAB represents the subscriber circuit output waveform.

Next, the operation will be explained. Set the power supply control terminal BN to “H”
When the current supply circuit BS (N) for normal power supply is in the power supply state and the current supply circuit BS (R) for reverse power supply is in the normal power supply state with power supply stopped, the current flows from terminal AA to terminal AA. BB
flows in the direction of When the power supply control terminal BN is set to "L level" and BR is set to "H level", the current supply circuit BS (N) for normal power supply is in the power supply stopped state, the current supply circuit for reverse power supply is in the reverse power supply state, and the current flows from terminal BB to terminal AA. When both the power supply control terminals BN and BR are set to the "L level", both current supply circuits are in an OFF state in which power supply is stopped, and the current becomes zero.

When transmitting the billing pulse, the power supply control terminal is controlled as described above to shift the operating state of the subscriber circuit from normal power supply to off state to reverse power supply to off state to normal power supply. At this time, the waveform of the current supply circuit output becomes a sharp waveform as shown in FIG. 3 WVCD, and noise is generated. Since the billing pulse is sent out during a call, it is necessary to prevent noise caused by polarity reversal.As shown in Figure 1, a billing filter FIL consisting of an inductance L and a capacitor C is used to smooth the waveform. It smoothed it out and removed noise. In the conventional configuration, (1) the inductance L is low due to the low cutoff frequency of the charging filter;
It is necessary to increase the inductance value of C and the capacitance value of capacitor C, and it is necessary to have a high withstand voltage, so the packaging density of the subscriber circuit cannot be increased;
(2) Diodes D1 and D2 are required to prevent the power supply transistor from being reverse biased due to lightning surges, etc.; (3) In the off state, the current flowing through the current supply circuit becomes zero, so the power supply transistor is turned off and the The current supply circuit becomes inoperable, and the 2-wire 4-wire conversion circuit HYB, which is normally built into the current supply circuit, cannot be used, and it is necessary to separately install a 2-wire 4-wire conversion circuit in front of the billing filter; (4 ) The two-wire and four-wire conversion circuit also performed a termination function for audio signals. This resulted in drawbacks such as the need for high voltage and large capacitance capacitors.

(Problems to be solved by the invention) The present invention eliminates these drawbacks, and controls the DC feedback circuit in the current supply circuit to slowly operate the rising and falling waveforms of the power supply, thereby sending out smooth charging pulses. At the same time, by flowing current between both current supply circuits even in the off state, the current supply circuit is brought into operation and the 2-wire 4-wire conversion circuit in the current supply circuit can be used.Details are shown below using the drawings. Explain.

(Structure and operation of the invention) FIG. 4 shows a first embodiment of the present invention.
is a public telephone, LN1 and LN2 are communication lines, SLIC
is the subscriber circuit, BSH (N) is the current supply circuit for normal power supply, BSH (R) is the current supply circuit for reverse power supply, BFN, BFR are the current control terminals, CDC is the DC feedback control terminal, BF is the power supply control terminal, 4WR is 4
4WS represents a 4-wire audio input terminal and a 4-wire audio output terminal.

FIG. 5 shows an example of the configuration of the current supply circuit used in FIG. 4. The difference from the conventional configuration shown in Figure 2 is as follows.
The two features include the provision of a mutual current setting circuit IM and the provision of a DC feedback control terminal CDC to provide a function to externally control the amount of feedback from the DC feedback circuit DC to the adder circuit. The other parts are the same as the conventional one shown in FIG. That is, the current supply circuit used in the present invention is a two-wire four-wire conversion circuit HYB,
DC feedback circuit DC, adder circuit Σ, mutual current setting circuit IM, at least operational amplifier OP/transistor
Consists of a constant current circuit consisting of TR and resistor RE.

FIG. 6 is a waveform diagram of each part for explaining the first embodiment, where WBF is a power supply control waveform, WBFN,
WBFR is the signal waveform that controls the DC feedback circuit of each current supply circuit, BSH (N), BSH (R)
is a waveform indicating the current supply status of both current supply circuits,
WVAB represents the output waveform of the subscriber circuit.

Next, the operation will be explained. The current supply circuit is terminal A,
Detects the voltage between terminal B and drives a constant current circuit consisting of operational amplifiers OPA and OPB and power supply transistors TRA and TRB via the DC feedback circuit DC to simulate the power supply resistance and supply DC power to the telephone side. Do the following. Here, negative DC voltage is applied to the B side.
Since V _RR is applied, current flows in the direction from the A side to the telephone side to the B side. The adder circuit Σ adds the output of the DC feedback circuit DC, the audio signal current from the 2-wire 4-wire HYB, and the mutual current from the IM to drive a constant current circuit. Since the magnitude of the current from the DC feedback circuit DC is controlled by the control signal from the DC feedback control terminal CDC, the current supplied to the telephone can be controlled. This feeding current is also proportional to the mutual current setting signal IM.

In the present invention, a subscriber circuit is constructed by connecting two of the above-mentioned current supply circuits with opposite polarity to each other.Next, the operation of transmitting a polarity reversal signal will be explained.

Set the power supply control terminal BF to "H level" to put both current supply circuits into operation state, and set the current control terminal BFN to "H level" and BFR to "L level" to put normal power supply current supply circuit BSH (N) into power supply state. , the current supply circuit BSH (R) for reverse power supply is placed in a constant current power supply state. Current supply circuit BSH for reverse power supply
If the current supplied from (R) is controlled by the signal from the DC feedback control terminal CDC so that it is less than the current supplied from the normal power supply current supply circuit BSH (N), the polarity of the power supply to the telephone is set to normal power supply. Therefore, current flows in the communication lines LN1 and LN2 from terminal AA to terminal BB. Current control terminal BFN is “L level”, BFR is “H level”
The current supply circuit for normal power supply BSH (N) is in a constant current supply state, and the current supply circuit for reverse power supply is in a constant current supply state.
When BSH (R) is in the power supply state, the polarity of the power supply to the telephone is reverse power supply, and the communication line LN1,
Current flows in LN2 from terminal BB to terminal AA direction. Both current control terminals BFN and BFR are “L level”
When both current supply circuits are in a constant current supply state, if the constant current values are both set to the same value, current will flow between both current supply circuits, but no current will flow through the communication line and the current will be in a non-power supply state (off). state).

As mentioned above, the current supply circuit is the communication line LN
1. Even if the current flowing through LN2 is zero, the constant current is the minimum current when the power supply transistor TRA,
Since it is guaranteed that the current flows to TRB, the transistor can operate regardless of the power supply state. Therefore, according to the first embodiment, it is possible to construct a subscriber circuit that can operate (transmit alternating current signals) regardless of the presence or absence of power supply or the presence or absence of current flowing through the communication line. Therefore, the two-wire and four-wire conversion circuit in the current supply circuit is always in operation, and there is an advantage that it is possible to terminate the audio signal, that is, to realize the internal termination function.

FIG. 7 shows a second embodiment of the present invention, in which S1
~S4 represents a switch, and SW represents a switch control terminal. Other symbols are the same as in FIG.

In this embodiment, a subscriber circuit is constructed by connecting each of the output terminals of the current supply circuit described in the first embodiment with reverse polarity via switches S1 to S4. 1st
It has the same configuration as the embodiment. The sending operation of the polarity reversal signal is the same as in the first embodiment. When the current control terminals BFN and BFR are both set to "L level" in a non-power state other than during a call, if there is an error in the mutual current settings of both current supply circuits, a current corresponding to the error will flow through the call line. , according to this embodiment, switches S1 to S
4, the current flowing through the communication line can be completely reduced to zero. In other words,
For example, during normal power supply or reverse power supply, such as during a phone call, turn on switches S1 to S4.
Turns off when in off state.

FIG. 8 shows the third embodiment, in which DS1 to DS4
represents a unidirectional conduction type semiconductor switch. Other symbols are the same as in FIG.

FIG. 9 shows an example of the configuration of the current supply circuit used in the third embodiment, and the symbols are the same as those in FIG. 5.

This embodiment uses the switch S explained in the second embodiment.
This embodiment has a configuration in which semiconductor switches DS1 to DS4 having unidirectional conduction characteristics are substituted for S1 to S4, for example, PNPN switch elements, and the sending operation of the polarity reversal signal is the same as in the second embodiment. Mutual current is from terminal A of current supply circuit BSH (N) for normal power supply to terminal B of current supply circuit BSH (R) for reverse power supply, and current for normal power supply from terminal A of current supply circuit BSH (R) for reverse power supply. Since the current flows in the direction of the terminal B of the supply circuit BSH (N), there is no problem even if the switch has unidirectional conduction characteristics or if the switch has asymmetric characteristics. Semiconductor switch DS1~
By controlling the conduction state of DS4 to turn off the second
Similar to the embodiment, the current flowing through the communication line during the off state can be completely reduced to zero. According to this embodiment, due to the rectifying action of the one-way conduction switch, current flows in the outflow direction through terminals A of the current supply circuits BSH (N) and BSH (R), and current in the inflow direction flows through terminal B, so that communication is possible. Even if a lightning surge etc. is applied to the line, reverse bias will not occur between the collectors and emitters of the power supply transistors TRA and TRB, and the diode to prevent reverse bias of the power supply transistors required in the conventional configuration can be removed. can.

FIG. 10 shows the fourth embodiment, in which FIL(N),
FIL(R) represents a low pass filter. Other symbols are the same as in FIG.

FIG. 11 is a waveform diagram of each part for explaining the fourth embodiment, WCDC (N) is the DC feedback control input waveform of the current supply circuit for normal power supply, WCDC
(R) represents the DC feedback control input waveform of the current supply circuit for reverse power feeding. Other symbols are the same as in FIG.

This embodiment uses the DC feedback control terminal of the first embodiment.
Low-pass filters FIL (N) and FIL (R) are installed between CDC and current control terminals BFN and BFR, and changes in current control signals WBFN and WBFR are smoothed through the filters, and current feedback is returned. It is configured to apply to the control terminal, and the current supply circuit BSH (N), BSH
(R) The current change during transition from the power supply state to the constant current power supply state and from the constant current power supply state to the normal power supply state is smoothed. According to this embodiment, it is possible to construct a subscriber circuit capable of sending a noise-free charge pulse to a telephone set. The filter in this embodiment can be a pulse or active filter composed of a capacitor (C) and a resistor R, and the conventional LC filter composed of an inductance (L) and a capacitor (C) can be downsized.

(Effects of the Invention) As explained above, according to the first embodiment, regardless of the presence or absence of power supply or the presence or absence of current flowing through the communication line,
There is an advantage that the subscriber circuit can be made operable and that a 2-wire 4-wire conversion circuit etc. provided in the current supply circuit can be used.

Further, according to the second embodiment, in addition to the advantages of the first embodiment, there is an advantage that the current flowing through the communication line can be completely turned off by a switch.

In addition to the advantages of the second embodiment, the third embodiment has the advantage that the rectifying action of the unidirectional conduction type switch allows the elimination of the diode for preventing reverse bias of the power supply transistor, which was necessary in the conventional configuration.
A further advantage is that a semiconductor switch suitable for integration can be used as the switch element.

Furthermore, according to the fourth embodiment, it is possible to achieve the same function as the billing pulse filter, which is composed of LC and required in the conventional configuration, using the CR filter, and there is an advantage that the filter can be made smaller. .
Furthermore, by employing the circuit configuration of the present invention, the circuit that smoothly sends billing pulses to public telephones, which was conventionally constructed using electromagnetic components, can be constructed from electronic circuits, making it possible to achieve high integration (LSI).

[Brief explanation of drawings]

FIG. 1 is an example of the configuration of a conventional subscriber circuit, FIG. 2 is an example of the configuration of a conventional current supply circuit, FIG. 3 is an explanatory diagram of the operation of the conventional subscriber circuit, and FIG. Embodiment, FIG. 5 is an example of the configuration of a current supply circuit, FIG. 6 is an explanatory diagram of the operation of the present invention, FIG. 7 is a second embodiment,
FIG. 8 shows the third embodiment, FIG. 9 shows an example of the configuration of the current supply circuit used in the third embodiment, FIG. 10 shows the fourth embodiment, and FIG. 11 explains the operation of the fourth embodiment. It is a diagram. Tel...Public telephone, SLIC...Subscriber circuit,
LN1, LN2...Telephone line, HYB...2-wire 4-wire conversion circuit, BS(N)...Current supply circuit for normal power supply, FIL...Charging filter, BS(R)...Current supply circuit for reverse power supply, BN, BR...Power supply control terminal, L...Inductance, C...Capacitor, S1 to S4...Switch, OPA, OPB...
Operational amplifier, DC...DC feedback circuit, Σ...addition circuit, TRA, TRB...power supply transistor,
REA, REB...Resistor, D1, D2...Power supply transistor reverse bias prevention diode, SO...
...Power supply control switch, BF...Control terminal, A, B
... Output terminal, BSH (N) ... Current supply circuit for normal power supply, BFN, BFR ... Current control terminal,
BSH (R)...Current supply circuit for reverse power supply,
CDC...DC feedback control terminal, 4WR...4-wire audio input terminal, IM...Mutual current setting signal, 4WS...
4-wire audio output terminal, FIL (N), FIL (R)...Filter, WBF...Power supply control waveform, WBN, WBR...
...Power supply control signal waveform, WBFN, WBFR...Current control signal waveform, WVAB...Output waveform, WVCD...
...Charging filter input waveform, WBS (N), WBS (R)
...Operating waveform of current supply circuit, WCDC (N),
WCDC(R)...DC feedback circuit control input waveform,
WBSH (N), WBSH (R)...Operating waveform of current supply circuit, SW...Switch control terminal.

Claims (1)

[Claims] 1. A 2-wire 4-wire conversion circuit that is connected to a 2-wire subscriber line and performs 2-wire/4-wire conversion of call signals;
a DC feedback circuit that is connected in parallel with the line conversion circuit to generate a first DC current; a switching circuit that turns on and off this DC current; and a DC feedback circuit that is connected in parallel with the line conversion circuit to generate a first DC current; a mutual current setting circuit that generates a second DC current that is always constant regardless of whether there is a call, and an audio signal current output from the two-wire four-wire conversion circuit and the first two adder circuits that add the direct current and the second direct current, and a first drive that amplifies the output current of the first adder circuit and supplies the direct current to one of the subscriber lines. and a second drive circuit that amplifies the output current of the second adder circuit and inputs a direct current from the other subscriber line, A subscriber circuit characterized in that a current supply circuit is connected with reverse polarity on the subscriber line side.