JPH0339428B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention [0001] The present invention relates to a communication current supply system for supplying direct current from an exchange to a home device for telephone calls, subscriber line monitoring, etc., and particularly relates to the configuration of the direct current supply circuit. It is.

BACKGROUND OF THE INVENTION FIG. 1 shows an example of the configuration of a current supply system in a subscriber line circuit.

In FIG. 1, 10 is a current supply circuit, 20 is a subscriber line, 30 is a telephone set, 101, 102, 10
3 is a resistance circuit, 104 is a battery, 105 is a ground, 1
06 and 107 are switches, 301 and 302 are resistors, and 303 and 304 are switches.

First, when supplying loop current, resistor circuit 1
01 and 102 to low resistance, switch 106
is connected to the contact a side and the switch 107 is turned on. The telephone 30 turns off the switch 303 and turns on the switch 304. In the following explanation, the circuit closed and open states of each switch are respectively turned on and off.
It's called off. As a result, ground 105 - resistance circuit 102 - switch 107 - terminal B - subscriber line 2
0 - Resistor 302 - Switch 304 - Subscriber line 20
A loop current flows through the path of - terminal A - switch 106 - resistance circuit 101 - battery 104.

Next, when supplying one-line current for detecting ground air on the A line on the terminal A side, such as when making an emergency call from a public telephone, the resistance circuit 103 is set to low resistance, and the switch 10 is turned on.
6 to the contact b side and turn off the switch 107. On the other hand, the telephone 30 has switches 303, 3
Turn on 04. As a result, the ground 105 - resistor 301 - switch 303 - subscriber line 20 - terminal A - switch 106 - resistor circuit 103 - battery 10
Direct current flows only on the A line side in path 4.

When making a normal call, a public phone turns on only the switch 304 in Figure 1 to create a route for current to flow between wires A and B. When making an emergency call, the caller turns on the switch by pressing the button for emergency calls. 3
In addition to 04, the switch 303 is also turned on, and one line is turned on. In order to detect this on the exchange side, it is necessary to have a function that allows current to flow toward the ground on one line while maintaining a state in which no loop current flows between the switch and the telephone, and to detect the ground current. functionality is required. In this way, when an emergency call is identified by the one-line current, it is possible to make a dial call without using coins as it is treated as non-billing. This is the reason why earth air detection is performed using single-wire current.

As described above, the conventional current supply method uses separate resistance circuits for flowing a loop current and for flowing a single-line current only on the A line, and a switch is used to switch between the two resistance circuits. was. Therefore, two types of resistance circuits and two switches are required.

On the other hand, there is a remote meter reading device (hereinafter referred to as a telemeter) that automatically measures and measures meters for water, gas, electricity, etc. from a remote location using a telephone line during free time when telephone subscribers are not making calls. When performing a silent call that starts without ringing the bell of the telephone, it is necessary to suppress the current flowing into the bell circuit of the telephone when the polarity of the DC voltage is reversed. For this reason, conventionally, in addition to a resistor circuit and a polarity inverting circuit, an integrating circuit consisting of a capacitor and a coil was included, making it difficult to downsize the current supply circuit.

Prior Art and Problems In digital exchanges that are currently in practical use, the network only allows digital signals to pass through. Therefore, this type of current supply circuit is
It is installed at the front of the network and must be installed individually for each subscriber line, and cannot be shared by multiple subscriber lines. Therefore, there is a strong demand for smaller and more economical devices.

Purpose of the Invention The present invention aims to make the device more compact and economical, and the present invention uses one type of resistor circuit to realize the functions of loop current supply, one-line current supply, stopping the communication current, and reversing the polarity of the communication current. The purpose of this device is to provide a system for supplying direct current to the telephone line through the device, which is more compact and economical, especially in digital exchanges.

Embodiment of the Invention FIG. 2 shows an embodiment of the invention, in which the same reference numerals as in FIG. 1 indicate the same parts. Further, 40 is a polarity inversion circuit, 60 is a timing control circuit, L and M are resistance value switching timing control signals of the resistance circuits 101 and 102, and O, N, and P are polarity inversion control signals of the polarity inversion circuit 40. In the present invention, the resistance circuit 10
1 and 102 can control high resistance and low resistance independently of each other.

Note that the resistance circuits 101 and 102 in the present invention are constant resistance circuits used in ordinary electronic subscriber circuits (for example, IEICE technical report SE80).
-39 “A study of IC-based subscriber circuits” Hamasato et al. 1980, 5
A circuit with a control signal input transistor added was used. FIG. 3 shows the resistance circuit 10.
1,102 is shown. 311 is a constant resistance circuit of the electronic subscriber circuit; 312 is a control signal input transistor; the emitter and collector terminals are connected in parallel with the resistor R1; the voltage between the base and emitter of the transistor 312 is controlled; By turning on and off the resistor circuit 10
Internal resistance value (impedance Ze) of 1,102
Switch. That is, by setting R1, R2≫RE, when the transistor 312 is on,
ZeR2, when off, becomes Ze〓〓R1+R2/R1・RE. (Ze=1/K ₁・RE/α, K ₁ = R1/R1+R2
It is. )I is a control signal input terminal, and O is an output terminal. Here, a control signal for turning the resistance circuits 101 and 102 on and off, that is, in a low-resistance and high-resistance state, is supplied from an ordinary control circuit on the exchange side.

First, the loop current is supplied as follows. Both resistance circuits 101 and 102 are placed in a first circuit state of low resistance. On the other hand, the telephone 30 is
Switch 303 is turned off and switch 304 is turned on. As a result, the ground 105-resistance circuit 102
- Polarity inversion circuit 40 - Terminal B - Subscriber line 20 - Resistor 302 - Switch 304 - Subscriber line 20 - Terminal A - Polarity inversion circuit 40 - Resistance circuit 101 - Battery 1
A loop current flows through the path 04.

Next, the single wire current is supplied as follows.
The resistance circuit 101 is switched to a second circuit state of low resistance and the resistance circuit 102 is switched to a high resistance state. On the other hand, telephone 3
0 turns on switches 303 and 304. As a result, the ground 105-resistor 301-switch 30
3-Subscriber line 20-Terminal A-Polarity inversion circuit 40-
Resistance circuit 101 - Path α of battery 104 and grounding 105 - Resistance circuit 102 - Polarity reversal circuit 40 -
Terminal B - Subscriber line 20 - Resistor 302 - Switch 3
04-Subscriber line 20-Terminal A-Polarity inversion circuit 40
A current flows through the path β between the resistance circuit 101 and the battery 104, but since the resistance circuit 102 has a high resistance, the current flowing through the path β is sufficiently smaller than the current flowing through the path α. Therefore, the state can be made almost equivalent to a state in which a one-line current is flowing.

By the way, there is a possibility that an invalid loop current may continue to flow for a long time due to a subscriber disconnecting the telephone receiver or the like. In order to suppress such reactive current, a function to stop the current supply is required. In the present invention, the resistance circuit 1
This function is achieved by switching both 01 and 102 to a high resistance third circuit state.

Next, FIG. 4 shows an example in which the current supply circuit according to the present invention is applied to a silent call of a telemeter. Fourth
In the figure, the same reference numerals as in FIG. 2 indicate the same parts.
31 is a telemeter, and a polarity reversing circuit 40 is composed of electronic switches 43 to 48 and resistors 49 and 50.

Ringless calling of the telemeter 31 is performed by reversing the voltage polarities of the A and B terminals. At this time, the bell of the telephone 30 may ring due to the charging/discharging current to the capacitor in the telephone 30. In order to prevent this, it is necessary to suppress the charging/discharging current to a small level when transmitting the polarity inversion signal.

FIG. 5 shows an example of a control sequence of the method for transmitting the polarity inversion signal using the circuit configuration shown in FIG. 4.

Initially, the control signals L, M, and N from the timing control circuit 60 are set to "High" (hereinafter referred to as "H"), and the control signals O and P are set to "Low" (hereinafter referred to as "L").
Both the resistance circuits 101 and 102 are in the first circuit state of low resistance, the switches 43 and 46 are on, and the switches 44, 45, 47, and 48 are off, and the battery 10
4-Resistance circuit 101-switch 43-terminal A path generates negative potential -V ₀ at terminal A and connects ground 1
05-Resistance circuit 102-Switch 46-Terminal B path is in a state where zero potential is generated at terminal B, and the voltage V _AB between terminals A and B is +V ₀ .
At this time, it is assumed that the DC loops of the telephone 30 and the telemeter 31 are in an open state and no DC loop current flows, and that the DC loops are also in an open state during the following circuit operation.

First, set the control signal P to "H" and switch 4.
Turn on 7,48. This allows grounding 105
- Resistance circuit 102 - Switch 46 - Resistance 50 - Switch 48 - Switch 43 - Resistance circuit 101 - Battery 104. A DC current flows through the path, and the voltage V _AB between terminals A and B is the terminal voltage of resistor 50 and switch 4.
The sum of the ON voltages of 8 is _V1 . Here, the resistance is 50
When is set to n ₁ times the resistance value of the resistance circuits 101 and 102 (the resistance values of the resistance circuits 101 and 102 are each 1), the following equation holds true. However, the on-voltage of the switch is omitted. The same applies below.

V ₁ =n ₁ /n ₁ +2V ₀ (1) Next, the control signal M is set to “L”, and the resistance circuit 10
2 to a second circuit state of high resistance. If the resistance value of the resistance circuit 102 at high resistance is set to n ₂ times the resistance value at low resistance, the voltage V _AB between terminals A and B is V ₂ shown in the following formula.
is given by

V ₂ =n ₁ /n ₁ +n ₂ +1V ₀ (2) Next, the control signals L, N, and P are set to “L”, and the resistance circuit 101 is switched to the third circuit state of high resistance,
Turn off switches 43, 46, 47, and 48.
As a result, the DC current becomes zero, and terminals A and B
The voltage between V _AB becomes zero.

Next, the control signals L and O are set to "H", the resistance circuit 101 is switched to the second low resistance circuit state, and the switches 44 and 45 are turned on. This allows grounding 1
05-Resistance circuit 102-Switch 45-Terminal A path with zero potential at terminal A, battery 104-Resistance circuit 1
01-Switch 44-Apply a negative potential to terminal B through the terminal B path, and change the voltage between terminals A and B from _zero to -V ₀
change to When this voltage change occurs, the telephone 30
A charging current flows through the capacitor in the capacitor, but since the resistance circuit 102 is in a high resistance state, the charging current can be kept small.

In this way, it is necessary to turn on the switches 44 and 45 while keeping the loop resistance of the power supply circuit 10 in a high resistance state. Since the switches 44 and 45 are electronic switches, in order to turn them on,
It is necessary to flow a gate current from the p-gate to the cathode or from the anode to the n-gate of each switch, but if the resistance circuits 101 and 102 both have high resistance, the gate current will not flow. Therefore,
By switching one of the resistance circuits 101 and 102 to a second circuit state in which the resistance is low and the other is high resistance, the gate current can be caused to flow. In other words, in order to prevent the bell inside the telephone 30 from ringing,
Set the loop resistance to high resistance state and switch 4
It is possible to satisfy the two conditions of securing the gate current necessary to guarantee the ON operation of 4 and 45.

FIG. 6 is an example of experimental results shown in response to changes in control signals L, M, N, O, and P. The required polarity reversal voltage waveform V _AB has been obtained, and switches 44 and 45
It can be seen that it is working normally. Further, it can be seen that the charging/discharging current I _A to the capacitor in the telephone 30 is suppressed to 2.5 mA or less, and a high resistance loop state is realized. According to another experiment, when polarity reversal is performed in a low resistance loop state, the charging/discharging current
It was confirmed that I _A reached approximately 10 mA.

Effects of the Invention As explained above, according to the present invention, the functions of loop current supply, one-line current supply, stop of call current, and polarity reversal in silent calling can be achieved in a single system without the need for multiple types of resistance circuits. DC current can be supplied to the telephone line through various types of resistive circuits. Therefore, the present invention is extremely effective as a communication current supply system in digital exchanges where miniaturization and economicalization of equipment are extremely important.

Furthermore, when using the circuit configuration shown in Fig. 4 as a method for transmitting the telemeter's silent ringing signal, the loop resistance is kept in a high resistance state.
This method has the advantage of minimizing the increase in the number of circuit elements as a method of securing the gate current necessary for turning on the electronic switch.

[Brief explanation of drawings]

Fig. 1 is an example of the configuration of a conventional current supply system, Fig. 2 is an embodiment of the current supply system according to the present invention, Fig. 3 is an embodiment of the resistance circuit according to the present invention, and Fig. 4 is a current supply according to the present invention. An example of a circuit configuration when the method is applied to a telemeter silent call, FIG.
An example of the control sequence of the telemeter silent call sending method using the circuit configuration shown in the figure, FIG.
This is an example of the figure. 10... Current supply circuit, 20... Subscriber line, 30...
Telephone, 101, 102, 103...Resistance circuit, 1
04...Battery, 105...Grounding, 106,107...Switch, 301,302...Resistance, 303,304
...Switch, 31... Telemeter, 43-48... Electronic switch, 49, 50... Resistor, 311... Constant resistance circuit of electronic subscriber circuit, 312... Transistor, 40... Polarity inversion circuit, 60... Timing control circuit.

Claims (1)

[Scope of Claims] 1. A communication current that connects the battery line side and the ground line side of the communication line to the battery and the earth through a resistance circuit, respectively, and supplies communication current to the in-home equipment via the battery line and the ground line. In the supply method, a pair of resistor circuits connected to the battery wire side and a ground wire side each switch internal resistance values to high resistance and low resistance by a control signal from a timing control circuit; and a polarity inverting circuit connected between the timing control circuit and the polarity inverting circuit that inverts the polarity of the DC voltage output from the resistor circuit in response to a control signal from the timing control circuit, and when supplying speech current to the speech line, the timing control circuit A loop current is supplied by switching to a first circuit state in which both of the pair of resistance circuits have low resistance in response to a control signal from the circuit, and the resistance circuit on the battery line side has low resistance and the resistance circuit on the ground line side has low resistance. By switching to a second circuit state in which the resistance circuit has a high resistance, a one-line current is supplied to the battery wire side, and a third state in which the pair of resistance circuits both have a high resistance is supplied.
When switching the circuit state to the first circuit state to stop the supply of communication current and invert the polarity of the DC voltage of the communication line, the control signal from the timing control circuit changes the circuit state of the pair of resistor circuits to the first circuit state. 1. A communication current supply system characterized in that after the circuit state is sequentially switched to a circuit state, a second circuit state, and a third circuit state, the polarity of the DC voltage is switched by the polarity reversing circuit.