JPH10257208A - Local power feeding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a permission value against the resistance of a subscriber line and to increase terminal equipments whose line resistance exceeds the permission value by a decrease number which can be stored in an exchange by terminating DC power supplied from an intra-station line terminating equipment to an intra- house line terminating equipment via the subscriber line in the local feeding means of low resistance from the intra-house line terminating equipment. SOLUTION: The local feeding means 600 is inserted into a connection point between the subscriber line 3 and the intra-house line terminating equipment 5. DC power supplied from the intra-station line terminating equipment 4 via the subscriber line 3 interrupts transmission to the intra-house line terminating equipment 5 and it is terminated by the DC terminating means in the local feeding means 600. DC power is supplied to the intra-house line terminating equipment 5 from the feeding means 602 in the local feeding means 600. Thus, the intra-house line terminating equipment 5 can receive DC power (DC current 39mA against an internal resistance 800Ω) required for an operation from the local feeding means 600 even if the line resistance value of the subscriber line 3 becomes 800Ω.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local power supply system in a subscriber line communication system, and more particularly to a terminal device via a metallic two-line subscriber line terminated by an intra-office line termination device and a home line termination device. And a local power supply system in a subscriber line communication system having a function of supplying DC power to a subscriber line terminal via a subscriber line.

[0002]

2. Description of the Related Art FIG. 7 is a diagram exemplifying a conventional subscriber line communication system, FIG. 8 is a diagram exemplifying an intra-office line termination device in FIG. 7, and FIG. FIG. 10 is a diagram illustrating the DC power supply state in FIG. 7.

[0003] In FIG. 7, when an exchange (1) constituting an integrated service digital network (ISDN) accommodates a terminal device (2) via a metallic two-wire subscriber line (3), an exchange is provided. The subscriber line (3) is composed of an intra-office line termination device (4) provided on the (1) side and a home line termination device (5) provided inside the house where the terminal device (2) is installed.
Is terminated, and the terminal device (2) is connected to the home line terminal device (5) by a four-wire terminal line (6).

[0004] The intra-office line termination device (4) and the home line termination device (5) are provided with a predetermined frequency required for the terminal device (2) to execute various communications via an integrated service digital network (ISDN). The band exchange signal is transmitted and received via the subscriber line (3).

[0005] The intra-office line termination device (4) is required for the operation of the in-home line termination device (5) and the terminal device (2) to the in-home line termination device (5) via the subscriber line (3). Supply of direct current power.

[0008] The intra-office line terminating device (4) and the in-home line terminating device (5) shown in FIGS. 8 and 9 mainly show a supply path of DC power. It has been simplified.

As shown in FIG. 8, an intra-office line termination device (4) includes an AC signal transmission / reception circuit (41), a power supply circuit (4).
2), current detection circuit (43), power supply polarity control circuit (4
4) and an AC / DC separation circuit (45).

[0008] Further, as shown in FIG. 9, an in-home line termination device (5) comprises an AC / DC separation circuit (51), a subscriber line interface circuit (52), and a terminal interface circuit (5).
3) a standby circuit (54), a call detection circuit (55), and a DC conversion circuit (56).

The AC signal transmitting / receiving circuit (41) in the intra-office line termination device (4) and the subscriber line interface circuit (52) and the terminal interface circuit (53) in the home line termination device (5) are the same as those described above. AC signal to subscriber line (3)
Send and receive via.

On the other hand, a power supply circuit (42) in the intra-office line terminal (4) receives direct-current power (DC ₁ ) from an exchange main power supply (for example, -48 volts) owned by the exchange ( ₁ ), and DC power (DC ₂ ) to be supplied to the line terminating device (5) is generated, and is passed through a current detection circuit (43), a power supply polarity control circuit (44), and an AC / DC separation circuit (45) to a subscriber line (DC). Send to 3).

The DC power (D) transmitted to the subscriber line (3)
C ₂ ) is supplied to the home line terminal (5) via the subscriber line (3). In the home line terminal (5), an AC / DC separation circuit (51) converts an AC signal and DC power (DC ₂ ) transmitted from the intra-office line terminal (4) via the subscriber line (3). And the AC signal is transferred only to the subscriber line interface circuit (52), and the DC power (DC ₂ ) is transferred to the standby circuit (54) and the DC conversion circuit (5).
6).

The diodes (D ₅₁ ) and (D ₅₂ ) added to the standby circuit (54) and the DC conversion circuit (5)
Diodes (D ₅₃ ) and (D ₅₄ ) added to 6)
Selects a supply destination according to the polarity of DC power (DC).

In the intra-office line terminal (4), the polarity of the DC power (DC) output from the power supply circuit (42) is controlled by a power supply polarity control circuit (44). When no signal is input from outside, the power supply polarity control circuit (44) outputs the DC power (DC ₂ ) output from the power supply circuit (42) without inverting the polarity, and as a result, The DC power (DC ₂ ) transmitted to the subscriber line (3) via the AC / DC separation circuit (45) is such that the A line side of the subscriber line (3) has a positive polarity (+) and the B line side has a negative polarity. (-) [Hereinafter referred to as normal polarity]
An incoming call detection signal (S) indicating that an incoming call to the terminal device (2) has been detected from a call processing unit (not shown) in the exchange (1).
_T ) or a call detection signal (S _O1 ), which is output from the current detection circuit (43) in a process described later and detects a call from the terminal device (2),
The DC power (DC ₂ ) output from the power supply circuit (42) is inverted and output, and as a result, the DC power (DC ₂ ) transmitted to the subscriber line (3) via the AC / DC separation circuit (45) is output. The polarity of DC ₂ ) is set to a negative polarity (−) on the A line side of the subscriber line (3) and a positive polarity (+) on the B line side (hereinafter referred to as reverse polarity).

The normal polarity DC power (DC ₂ ) is called normal power (DC _2N ), and the reverse polarity DC power (DC ₂ ) is called reverse power (DC _2R ).
Therefore, when a call is not set up to the terminal device (2), the local line termination device (4) switches to the subscriber line (3).
The normal line power (DC _2N ) is supplied to the in-home line termination device (5) via the terminal, and in the state where either the outgoing call or the incoming call is generated to the terminal device (2), the intra-office line termination is performed. Reverse power (DC _2R ) is supplied from the device (4) to the home line terminal (5) via the subscriber line (3).

In the home line terminal (5), the
From the line termination device (4) via the subscriber line (3)
Maru power (DC_2N) Is supplied when the diode
(D ₅₁) And (D₅₂) Is forward biased, diode
(D₅₃) And (D₅₄) Is reverse biased,
-Mal power (DC_2N) Is supplied to the standby circuit (54)
It will be.

The calling detection circuit (55) in the home line terminal (5) determines the calling state of the terminal device (2) accommodated in the home line terminal (5) by the terminal line (6). TA
Monitors via line and TB line, when no detect a call of the terminal device (2), predetermined termination resistors standby circuit (54) (R ₅₄₎ relative to the normal power (DC _2N) Is set to a high resistance value (for example, several thousand ohms), but in a state where the calling of the terminal device (2) is detected, the terminating resistance (R54) of the standby circuit ( ₅₄ ) is set to a predetermined low resistance value [ For example, 800 ohms].

On the other hand, when the load resistance is not more than 1600 ohms, the power supply circuit (42) in the intra-office line termination device (4) outputs a substantially constant DC current (for example, about 39 mA DC), and outputs the load resistance. Increases above 1600 ohms, the output current (I _DC2 ) drops sharply [eg 1
8 mA or less], and the output voltage converges to a predetermined value (for example, 60 VDC).

Therefore, in the state where normal power (DC _2N ) is output from the intra-office line termination device (4) and terminated by the standby circuit (54) in the intra-home line termination device (5), the intra-home line termination device ( in a state where 5) the terminal device accommodated in (2) is not a call, the terminating resistor (R ₅₄ standby circuit (54)) because it is set to thousands ohms as described above, the feed circuit (42) Has a load resistance of 1600 ohms or more, and the output current (I _DC2 ) from the power supply circuit (42)
Is 18 mA or less as described above (see FIG. 10A).

The home line terminal (5) in this state is
DC power required for the operation is not supplied, and the apparatus is set to the standby state. In this state, when the terminal device accommodated in the home network unit (5) (2) is a calling state, the terminating resistor of the standby circuit (54) (R ₅₄₎ because it is set to 800 ohms as described above When the line resistance (R _L ) of the subscriber line (3) is equal to or less than 800 ohms, the load resistance value of the power supply circuit (42) is equal to or less than 1600 ohms,
The output current (I _DC2 ) from the power supply circuit (42) is about 39
The result is a milliamp (see FIG. 10B).

The current detection circuit (43) in the intra-office line termination device (4) monitors the output current (I _DC2 ) of the power supply circuit (42), and the current value is less than a predetermined value (for example, 26 mA). In this case, it is determined that the in-home terminal unit (5) has not detected the call from the accommodation terminal device (2), but if the current value exceeds a predetermined value (26 milliamps in the above-mentioned case), The line termination device (5) is the accommodation terminal device (2)
The power supply polarity control circuit (44)
A call detection signal (S _O1 ).

The power supply polarity control circuit (44) which has received the call detection signal (S _O1 ) inverts the DC power (DC ₂ ) output from the power supply circuit (42) from the normal polarity to the reverse polarity, and performs AC / DC separation. Subscriber line (3) via circuit (45)
Is supplied with reverse power (DC _2R ).

In the home line terminal (5), when reverse power (DC _2R ) is supplied from the intra-office line terminal (4) via the subscriber line (3), the diodes (D ₅₃ ) and (D ₅₃ ) D ₅₄ ) is in a forward bias state, and the diodes (D ₅₁ ) and (D ₅₂ ) are in a reverse bias state, so that DC power (DC ₂ ) is supplied to the DC conversion circuit (56).

The terminal resistance (R ₅₆ ) of the DC conversion circuit ( ₅₆ )
Is also set to approximately 800 ohms, so the output current (I _DC2 ) from the power supply circuit (42) of the intra-office line termination device (4)
Is maintained at 39 mA and the current detection circuit (4
3) transmits the call detection signal (S _O1 ) to the power supply polarity control circuit (4).
4), and the reverse power (DC _2R ) is continuously supplied from the intra-office line termination device (4) to the subscriber line (3).

The DC conversion circuit (56) converts the reverse power (DC _2R ) supplied from the intra-office line termination device (4) via the subscriber line (3) into each of the signals in the home line termination device (5). DC + 5V DC power used in circuit (DC ₃ )
And a DC power (DC ₄ ) of +40 volts DC used in the terminal device (2), and a home line termination device (5)
To each circuit and the terminal device (2) [FIG.
(c)).

As described above, the terminal device (2) and the private line terminal (5) shift from the standby state to the operating state, and the subscriber line interface circuit (52) and the terminal interface circuit in the private line terminal (5). (53) and an AC signal transmitting / receiving circuit (41) in the intra-office line termination device (4)
A predetermined AC signal is transmitted / received via the subscriber line (3), and the exchange (1) starts calling processing of the terminal device (2).

On the other hand, when an incoming call to the terminal device (2) occurs in the exchange (1), as described above, a call processing unit (not shown) in the exchange (1) sends an intra-office line termination device ( 4) of the power supply polarity control circuit (44) for an incoming call detection signal (S _T) is transmitted, the power supply polarity control circuit (44)
Is the DC power (DC ₂ ) output from the power supply circuit (42)
Is inverted from the normal polarity to the reverse polarity, and reverse power (DC _2R ) is supplied to the subscriber line (3) via the AC / DC separation circuit (45).

When the reverse power (DC _2R ) starts to be supplied from the intra-office line termination device (4) via the subscriber line (3), the in-home line termination device (5) supplies the reverse power (DC _2R ). The received DC conversion circuit (56) generates DC power (DC ₃ ) of DC +5 volts and DC power (DC ₄ ) of DC +40 volts in the same manner as described above, and the in-home line termination device (5) And the terminal (2) [see FIG. 10 (c)].

As described above, the terminal device (2) and the private line termination device (5) are activated, and the subscriber line interface circuit (52) and the terminal interface circuit (53) in the private line terminal device (5) A predetermined AC signal is transmitted / received to / from an AC signal transmission / reception circuit (41) in the intra-office line terminal (4) via the subscriber line (3), and the exchange (1) is transmitted to the terminal device (2). Is executed.

[0029]

As is apparent from the above description, in the conventional subscriber line communication system, the intra-office line termination device (4) and the in-home line termination device (5) have a line resistance (R _L ). Are designed for subscriber lines (3) of 800 ohms or less.

On the other hand, the attenuation of the subscriber line (3) with respect to the AC signal transmitted and received between the intra-office line termination device (4) and the home line termination device (5) is allowed to be about 50 dB. In order to use the subscriber line (3) having such an attenuation, the line termination (4) in the office and the line termination (5) in the home must have a line resistance (R _L ) of up to 1500 ohms.
It is necessary to enable the subscriber line (3) having

Therefore, in order to accommodate the terminal equipment (2) having the line resistance (R _L ) of the subscriber line (3) exceeding 800 ohms in the exchange (1), the existing intra-office line termination equipment (4) and There was a problem that the home terminal unit (5) could not be used.

An object of the present invention is to make it possible to accommodate, in an exchange, a terminal device in which the line resistance of a subscriber line exceeds an allowable value by using an existing intra-office line termination device and home line termination device.

[0033]

FIG. 1 is a diagram illustrating the principle of the present invention. In FIG. 1, 1 is an exchange, 2 is a terminal device, 3 is a metallic two-wire subscriber line, 4 is an intra-office line termination device,
Reference numeral 5 denotes an in-home line termination device.

Reference numeral 600 denotes a local power supply unit inserted at the connection point between the subscriber line (3) and the home line terminal (5) according to the present invention. 601 is an AC / DC separation unit provided in the local power supply unit (600) according to the present invention.

Reference numeral 602 denotes a local power supply means (6
00). 603 is a DC termination means provided in the local power supply means (600) according to the present invention.

Reference numeral 604 denotes a power supply state control means provided in the local power supply means (600) according to the present invention (claim 2). Reference numeral 605 denotes a terminal call detection means provided in the local power supply means (600) according to the present invention (claim 3).

Reference numeral 606 denotes a call state transfer means (606) provided in the local power supply means (600) according to the present invention (claim 3). Metallic two-line subscriber line (3)
Switch (1) through one end of the intra-office line termination device (4)
, And a terminal device (2) is connected to the other end of the subscriber line (3) via a home line terminal (5) to form a subscriber line communication system.

The intra-office line termination device (4) supplies predetermined DC power via the subscriber line (3) to the home line termination device (5).
With a function to supply to the home, and a home line terminal (5)
Has a function of receiving and operating the DC power supplied via the subscriber line (3), and furthermore, the local line terminal (4) and the home line terminal (5) are An AC signal in a predetermined frequency band is transmitted and received via the line (3).

The power supply means (602) supplies DC power required for the operation of the home line terminal (5). DC terminating means (603) converts DC power supplied from the intra-office line terminating device (4) via the subscriber line (3) to a terminating resistor for the subscriber line (3) of the home line terminating device (5). Terminate with lower resistance.

The AC / DC separation means (601) supplies an AC signal transmitted and received via the subscriber line (3) between the intra-office line termination device (4) and the home line termination device (5). (602) and the DC termination means (603), and the DC power supplied from the intra-office line termination device (4) via the subscriber line (3) is transmitted to the home line termination device (5). ) Is transmitted to the DC terminal means (603) while being prevented from being transmitted to the connection terminal of the subscriber line (3), and the DC power supplied from the power supply means (602) to the home line terminal (5) is: Prevents transmission to subscriber line (3).
[The present invention (claim 1)] Note that the DC termination means (603) has a built-in power supply polarity discriminating function for supplying DC power supplied from the intra-office line termination device (4) via the subscriber line (3). When it is determined that the polarity of the power supply has been inverted, it is considered that the termination resistance value is changed between the non-inverted state and the inverted state [the present invention (claim 2)]. A power supply polarity identification function for identifying the polarity of the DC power supplied from the intra-office line termination device (4) via the subscriber line (3) is provided in the DC termination means (603). Power supply state control means (604) for controlling the polarity of the DC power supplied from the power supply means (602) to the subscriber line (3) connection terminal of the home line terminal (5) based on the voltage polarity of the DC power identified by ) Is considered. [Invention (Claim 3)] Further, the local power supply means (600) monitors the DC current supplied from the power supply means (602) to the home line termination device (5) and is accommodated in the home line termination device (5). Terminal call detecting means (605) for detecting a call from the terminal device (2), and DC terminal means (605) when the terminal call detecting means (605) detects a call from the accommodated terminal device (2). It is considered that call state transfer means (606) for changing the terminating resistance value of DC power supplied from the intra-office line terminating device (4) via the subscriber line (3) according to 603) is added. [Invention (Claim 4)] Therefore, the home line termination device is supplied with required DC power from local power supply means inserted at the connection point with the subscriber line. And always receive the necessary and sufficient supply of DC power In addition, the DC power supplied from the intra-office line termination device to the in-home line termination device via the subscriber line is terminated by the local power supply means having a lower resistance than the in-home line termination device. Without changing the DC power that can be transmitted to the subscriber line, the allowable value for the line resistance of the subscriber line can be increased by the decrease in the terminating resistance, and the existing intra-office line termination device and home line termination device can be used. As a result, a terminal device having a line resistance of a subscriber line exceeding an allowable value can be accommodated in the exchange, and the accommodation range of the terminal device can be expanded.

[0041]

Embodiments of the present invention will be described below with reference to the drawings. 2 is a diagram illustrating a subscriber line communication system according to an embodiment of the present invention, FIG. 3 is a diagram illustrating a local power supply circuit in FIG. 2, and FIGS. 4 to 6 are diagrams illustrating a DC power supply situation in FIG. FIG. The same reference numerals indicate the same objects throughout the drawings.

In FIG. 2, a local power supply circuit (7) is inserted as a local power supply means (600) in FIG. 1 at a connection point between a subscriber line (3) and a home terminal unit (5).

The intra-office line termination device (4) in FIG.
The home terminal unit (5) is the same as that shown in FIGS. 8 and 9, respectively. The local power supply circuit (7) has a configuration as shown in FIG. 3, and is provided with an AC / DC separation circuit (71) as the AC / DC separation means (601) in FIG.
A power supply circuit (72) is provided as 2), and a DC termination circuit (7) is used as the DC termination means (603) in FIG.
3), a power supply polarity relay circuit (74) is provided as power supply state control means (604) in FIG. 1, and a current detection circuit (75) is provided as terminal call detection means (605) in FIG. The call notification circuit (7) serves as a call state transfer means (606) in FIG.
6) is provided.

The power supply circuit (72) is replaced by the in-home line terminal (5) instead of the DC power (DC ₂ ) supplied from the in-station line terminal (4) via the subscriber line (3). which home network unit (5) and the terminal device (2) is a direct current power (DC ₅₎ that needs to operate, is supplied to the connection terminals of the subscriber line (3) in a house line terminal devices (5) Thus, it has substantially the same performance as the power supply circuit (42) in the intra-office line termination device (4).

The DC termination circuit (73) is a current detection circuit
(731) and (732), a diode (D₇₁) And
(D₇₂) And a resistor (R₇₁) Through (R₇₃)
And a diode (D₇₁) Is for home line termination (5)
Diode (D₅₁) And (D₅₂Played the role of
And a diode (D₇₂) Is for home line termination (5).
Diode (D₅₃) And (D₅₄Played the role of
And the resistance (R₇₁) And (R₇₂) Is the intra-office line termination device
Norma supplied from (4) via subscriber line (3)
Power (DC_2N) In the home line terminal (5)
Standby circuit (54) [Terminal resistor (R₅₄)] Instead of termination
The resistance (R₇₃) Is the intra-office line termination device
River supplied from (4) via subscriber line (3)
Power (DC _2R) In the home line terminal (5)
Plays the role of terminating instead of DC conversion circuit (56)
You.

The resistance values of the resistors (R ₇₁ ) and (R ₇₃ ) are determined by the standby circuit (54) when the call detection signal is transmitted from the call detection circuit (55) and the DC conversion circuit (56). terminating resistor with (R ₅₄₎ and compared with (R ₅₆₎ [800 ohms in the previous] is set to a sufficiently low resistance value [for example, about 100 ohms, and resistor (R ₇₂₎ is a call detection When the call detection signal is not transmitted from the circuit (55), the resistance value of the standby circuit (54) is set to substantially the same value as the terminating resistance ( _R54 ) (several thousand ohms in the above description).

Further, the current detection circuits (731) and (73)
2) is connected to the diodes (D ₇₁ ) and (D ₇₂ ), respectively, and performs a power supply polarity discriminating function built in the DC termination means (603) in FIG.

The AC / DC separation circuit (71) includes the capacitors (C ₇₁ ) and (C ₇₂ ) and the blockage loops (L ₇₁ ) to (L ₇₁ ).
₇₄ ) and capacitors (C ₇₁ ) and (C
₇₂ ) is a power supply circuit (42) in the intra-office line termination device (4).
Power (D) supplied from the subscriber line (3)
DC power supplied from the power supply circuit (72) to the subscriber line (3) connection terminal of the home line termination (5), while preventing the transmission of C ₂ ) to the home line termination (5). (DC ₅ ) is prevented from being transmitted to the subscriber line (3), and an AC signal transmitting / receiving circuit (41) in the local line terminal (4) and a subscriber in the home line terminal (5) are prevented. to conduct an AC signal that is exchanged between the line interface circuit (52), also塞流line wheels (L ₇₁₎ and (L ₇₂₎ is an AC signal described above is transmitted to the DC termination circuit (73) And the DC power (DC ₂ ) supplied from the power supply circuit (42) via the subscriber line (3) to the DC termination circuit (7).
3), and the occlusion loops (L ₇₃ ) and (L ₇₄ )
Prevents the above-mentioned AC signal from being transmitted to the power supply circuit (72), and converts the DC power (DC ₅ ) output from the power supply circuit (72) to the subscriber line ( ₅ ) of the home terminal unit (5). 3) To supply to the connection terminal.

In FIG. 2 to FIG. 6, when no outgoing or incoming call occurs to the terminal device (2) via the subscriber line (3), the intra-office line termination device (4) joins. The normal line (3) is supplied with the normal polarity DC power (DC ₂ ) as described above.

In the local power supply circuit (7), when normal power (DC _2N ) is supplied from the intra-office line termination device (4) via the subscriber line (3), the direct current termination circuit (73)
The diode (D ₇₁ ) is in a forward bias state, the diode (D ₇₂ ) is in a reverse bias state, and the normal power (DC
_2N) is terminated by a resistor connected in series in the DC termination circuit (73) (R ₇₁₎ and (R _72).

In such a state, the intra-office line termination device (4)
DC current (I _NI2 ) supplied from the terminal has a low current value (18 mA or less in the above _description ), and the current detection circuit (43) in the intra-office line termination device (4) supplies the call detection signal (S _O1 ) with the power supply polarity. Without transmitting to the control circuit (44), the power supply polarity control circuit (44) holds the DC power (DC ₂ ) output from the power supply circuit (42) at the normal polarity.

The current detection circuit (731) in the DC termination circuit (73) uses the normal power (DC _2N ) supplied from the intra-office line termination device (4) to _connect the series resistors (R ₇₁ ) and (R ₇₂ ). The DC current (I _NI2 ) flowing through the power supply polarity relay circuit (74) and the control unit (761) in the call notification circuit (76) are detected by a current detection signal (I _NI2 ). S _N1 ) and (S _N2 ) are transmitted, and the current detection circuit (732) uses the normal power (DC _2N ) supplied from the intra-office line termination device (4) to set the resistance (R ₇₃ ).
Since the DC current ( _IR2 ) does not flow through the power supply polarity relay circuit (74), the current detection signal ( _SR1 )
Do not communicate.

As a result, in the power supply polarity relay circuit (74), the current detection signal (S
_The control unit (741) to which _N1 ) has been transmitted sets the corresponding connection units (742) and (743) to the conducting state,
The control unit (744) to which the current detection signal (S _R1 ) is not transmitted from the current detection circuit (732) is connected to the corresponding connection unit (74).
5) and (746) are set to the cutoff state.

As a result, the power supply polarity relay circuit (74)
The DC power (DC ₅ ) output from the power supply circuit (72) is set to normal polarity, and the A-line connection terminal of the subscriber line (3) connection terminal of the home line terminal (5) has a positive polarity (+).
Is connected to the B-line connection terminal by the negative power (−) normal power (DC
_5N ) supply.

In the home line terminal (5), normal power (DC _5N ) is supplied from the local power supply circuit (7) to the connection terminal of the subscriber line (3) of the home line terminal (5). , The call detection circuit (55) is the accommodation terminal device (2).
In the state where the call from is not detected, as described above,
Normal power (DC) supplied from the local power supply circuit (7)
The _5N), terminated by waiting circuit that is set to (54) [several thousand ohms in the previous] terminating resistor (R ₅₄₎ is a high resistance value.

In this state, the output current (I _DC5 ) from the power supply circuit (72) in the local power supply circuit (7) has a predetermined value, similarly to the power supply circuit (42) in the intra-office line termination device (4). Or less (ie 18 milliamps or less)
The current detection circuit (75) in the local power supply circuit (7) sends the call detection signal (S _O2 ) to the call notification circuit (76) in the same manner as the current detection circuit (43) in the local line termination (4). ) Are not transmitted to the control unit (761).

The control section (761) includes a current detection circuit (7
In a state where the call detection signal (S _O2 ) is not transmitted from 5), the corresponding connection section (762) is set to the cut-off state. When the connection part (762) is set to the cut-off state, the resistance (R ₇₂ ) in the DC termination circuit (73) is not short-circuited. ) normal power supplied via the (DC _2N) the series resistance in the DC termination circuit (73) (R ₇₁₎ and (R
₇₂ ) (see FIG. 4).

[0058] In this state, when the terminal device accommodated in the home network unit (5) (2) is a calling state, the termination resistance value of the standby circuit (54) (R ₅₄₎ is a low resistance [in above 800 ohm], the load resistance of the power supply circuit (72) in the local power supply circuit (7) is approximately 800 ohms, and the DC current (I _{NO 5} ) output from the power supply circuit (72) is about 39 mA and the DC current (I
_When the DC current (I _NO5 ) exceeds a predetermined value (26 mA in the above case), the current detection circuit (75) monitoring the _NO.5 signal is sent to the control unit (761) in the call notification circuit (76). A call detection signal (S _O2 ) is transmitted.

The control section (761) includes a current detection circuit (73)
When the call detection signal (S _O2 ) transmitted from the current detection circuit (75) is further received while the current detection signal (S _N2 ) transmitted from 1) is received, the connection portion (762) is turned on. , The resistance (R) in the DC termination circuit (73)
₇₂ ) will be short-circuited.

In this state, the intra-office line termination device (4)
The normal power (DC _2N ) supplied via the subscriber line (3) from the DC power supply is connected to a resistor (R ₇₁ ) in the DC termination circuit (73).
The termination resistance value is determined by the internal resistance value of the current detection circuit (731) and the diode (D
_If the forward resistance value of ₇₁ ) is neglected, it becomes about 100 ohm.

In this state, if the line resistance (R _L ) of the subscriber line (3) is 1500 ohms or less, the load resistance value of the power supply circuit (42) in the intra-office line termination device (4) becomes 1600. Ohms or less, the output current (I _DC2 ) from the power supply circuit (42) is about 39 milliamps, and the current detection circuit (43) in the intra-office line termination device (4) is connected to the home line termination device (43) in the same manner as described above. 5) determines that a call from the accommodation terminal device (2) has been detected, and transmits a call detection signal (S _O1 ) to the power supply polarity control circuit (44) (see FIG. 5).

The power supply polarity control circuit (44), which has received the call detection signal (S _O1 ), _supplies the power supply circuit (42) in the same manner as described above.
The output direct current power (DC _2), inverted from the normal polarity to reverse polarity.

In the local power supply circuit (7), when reverse power (DC _2R ) is supplied from the intra-office line termination device (4) via the subscriber line (3), the DC termination circuit (73)
The diode (D ₇₂ ) is in a forward bias state, the diode (D ₇₁ ) is in a reverse bias state, and the reverse power (DC
_2R) is terminated by a resistor (R ₇₃₎ in the DC termination circuit (73).

[0064] The resistance value of the resistor (R _73), DC current resistance because it is set to (R ₇₁₎ equally 100 ohms, reverse power (DC _2R) supplied from the intra-station line terminal (4) ( I _R2 ) is maintained at a predetermined current value (approximately 39 milliamps in the above description) as described above, and the current detection circuit (43) in the intra-office line termination device (4) continues the call detection signal (S _O1 ). The power is transmitted to the power supply polarity control circuit (44), and the power supply polarity control circuit (44) holds the polarity of the DC power (DC ₂ ) output from the power supply circuit (42) at the reverse polarity.

In the DC termination circuit (73) in the local power supply circuit (7), the current detection circuit (732) includes a DC power (DC ₂ ) supplied from the intra-station line termination device (4).
As a result, the DC current (I _R2 ) flowing through the resistor (R ₇₃ ) is detected, and the current detection signal (S _R1 ) is transmitted to the control section (744) in the power supply polarity relay circuit (74). 7
31), the direct current (I _NO2 ) does not flow through the resistor (R ₇₁ ) depending on the reverse power (DC _2R ) supplied from the intra-station line termination device (4).
Control unit (741) and call notification circuit (76) in 4)
The current detection signals (S _N1 ) and (S _N2 ) are not transmitted to the control section (761).

As a result, in the power supply polarity relay circuit (74), the current detection signal (S
_The control unit (744) to which _R1 ) has been transmitted sets the corresponding connection units (745) and (746) to the conducting state.
The control unit (741) that has stopped transmitting the current detection signal (S _N1 ) from the current detection circuit (731) sets the corresponding connection units (742) and (743) to the cutoff state.

As a result, the power supply polarity relay circuit (74)
DC power (DC ₅ ) output from the power supply circuit (72)
Is changed from the normal polarity to the reverse polarity, the negative polarity (-) is connected to the A-line connection terminal of the subscriber line (3) connection terminal of the home line terminal (5), and the positive polarity (+) is connected to the B-line connection terminal. )
Supplies reverse power (DC _5R ).

In the home terminal unit (5), when reverse power (DC _5R ) is supplied from the local power supply circuit (7) to the connection terminal of the subscriber line (3), the direct current conversion circuit (5).
6).

The terminal resistance (R ₅₆ ) of the DC conversion circuit ( ₅₆ )
Is also set to approximately 800 ohms, so that the direct current (I) output from the power supply circuit (72) of the local power supply circuit (7) is
_R5 ) is maintained at 39 mA.

The DC conversion circuit (56) converts the reverse power (DC _5R ) supplied from the local power supply circuit (7) to the connection terminal of the subscriber line (3) from each circuit in the home terminal unit (5). To generate DC power (DC ₃ ) and (DC ₄ ) of DC +5 volts used in the terminal device (2) and DC +40 volts used in the terminal device (2). It is supplied to the terminal device (2) (see FIG. 6).

As described above, the terminal device (2) and the private line termination device (5) are activated, and the subscriber line interface circuit (52) and the terminal interface circuit (53) in the private line terminal device (5) A predetermined AC signal is sent to and from an AC signal transmission / reception circuit (41) in an intra-office line termination device (4) by a local power supply circuit (7) and a subscriber line (3).
The exchange (1) is transmitted and received via the terminal device (2)
The call processing of is started.

On the other hand, when an incoming call to the terminal device (2) occurs in the exchange (1), as described above, the call processing unit (not shown) in the exchange (1) sends an internal line termination device ( 4) of the power supply polarity control circuit (44) for an incoming call detection signal (S _T) is transmitted, the power supply polarity control circuit (44)
Is the DC power (DC ₂ ) output from the power supply circuit (42)
Is inverted from the normal polarity to the reverse polarity, and reverse power (DC _2R ) is supplied to the subscriber line (3) via the AC / DC separation circuit (45).

In the local power supply circuit (7), when reverse power (DC _2R ) is supplied from the intra-office line termination device (4) via the subscriber line (3), as described above, the DC termination circuit ( 73) through the diode (D ₇₂ ) in the resistor (R ₇₂ ).
₇₃ ), and the current detection circuit (73)
2) is a control unit (744) in the feeding polarity relay circuit (74)
Current detection signal (S _R1) begins to transmit, the current detection circuit (731) is a current detection signal to the control unit (741) to (S _N1)
Is transmitted, the control unit (744) sets the corresponding connection units (745) and (746) to the conductive state, and the control unit (741) sets the corresponding connection units (742) and (7).
43) is set to the blocking state, as a result, power supply polarity relay circuit (74), the polarity of the DC power output from the power supply circuit (72) (DC _5), set change from the normal polarity reverse polarity.

In the home line terminal (5), when reverse power (DC _5R ) is supplied from the local power supply circuit (7) to the connection terminal of the subscriber line (3), a DC conversion circuit is provided in the same manner as described above. (56) receives power, and the terminating resistance (R ₅₆ ) of the DC conversion circuit (56) is also set to approximately 800 ohms, so that the output current (from the power supply circuit (72) of the local power supply circuit (7)) I _DC5 ) is maintained at 39 mA.

The DC conversion circuit (56) converts the reverse power (DC _5R ) supplied from the local power supply circuit (7) to the connection terminal of the subscriber line (3) from each circuit in the home line terminal (5). To generate DC power (DC ₃ ) and (DC ₄ ) of DC +5 volts used in the terminal device (2) and DC +40 volts used in the terminal device (2). It is supplied to the terminal device (2) (see FIG. 6).

As described above, the terminal device (2) and the private line termination device (5) are activated, and the subscriber line interface circuit (52) and the terminal interface circuit (53) in the private line terminal device (5) A predetermined AC signal is sent to and from an AC signal transmission / reception circuit (41) in an intra-office line termination device (4) by a local power supply circuit (7) and a subscriber line (3).
The exchange (1) is transmitted and received via the terminal device (2)
Executes incoming call processing to.

As is apparent from the above description, according to the embodiment of the present invention, the local power supply circuit (7) is inserted at the connection point between the subscriber line (3) and the home line terminal (5), and DC power (DC ₂ ) supplied from the line terminating device (4) via the subscriber line (3) is converted into a home line terminating device (5).
To the home line termination device (5) from the power supply circuit (72) in the local power supply circuit (7). (DC ₅ ) is supplied, and even if the line resistance value of the subscriber line (3) becomes 800 ohm or more, the local line terminal (5) is required to operate from the local power supply circuit (7). DC power (DC ₅ ) (in the above description, DC current of 39 mA for an internal resistance of 800 ohms) is received.

The current detection circuit (75) and the call notification circuit (76) reliably detect the calling state of the terminal device (2) detected by the home terminal device (5) and perform a direct current termination circuit (73). ) controls the terminating resistor (R ₇₁ + R ₇₂₎ of the via subscriber line (3) from the intra-station line terminal (4) normal power (DC _2N) is supplied, the calling terminal device (2) In the state where no call is detected, the terminal is terminated by a series resistor ( _R71 + _R72 ) (that is, several thousand ohms). In the state where the call of the terminal device (2) is detected, only the resistor ( _R71 ) (that is, about 100
Ohm], and a reverse power (D) from the intra-office line termination device (4) via the subscriber line (3).
_C2R ), the resistance ( _R73 ) [i.e. about 1
00 ohm], the intra-office line terminating device (4) can reliably detect a call from the terminal device (2) until the line resistance of the subscriber line (3) reaches 1500 ohm. After the call detection of the terminal device (2) and the occurrence of the incoming call, the DC current (I
_NO2) or (I _R2), can be supplied via a subscriber line (3).

FIGS. 2 to 6 are merely one embodiment of the present invention. For example, the configuration of the local power supply circuit (7) is not limited to that shown in FIG. Is considered, but the effect of the present invention does not change in any case.

For example, when the subscriber line (3) is operated as a dedicated line, the DC power supply to the home line terminal (5) is executed only while a call is generated to the terminal device (2). It is not limited to what is performed, and continuous execution is also considered.

In such a case, the intra-office line termination device (4)
Supplies the DC power (DC) of the reverse polarity at all times, the local power supply circuit (7) terminates the DC power (DC) by the resistor (R ₇₃ ) in the DC termination circuit (73), and the power supply circuit (72) The DC power (DC) having the reverse polarity is fixedly supplied to the home line termination device (5), and the normal polarity DC power (DC) termination circuit [diode (D ₇₁ )] in the DC termination circuit (73) is provided. , Current detection circuit (73
1), resistors (R ₇₁ ) and (R ₇₂ )], the power supply polarity relay circuit (74), the current detection circuit (75), and the call notification circuit (76) can be omitted. Embodiment of Claim 1)], the effect of the present invention does not change even in such a case.

In the case where the subscriber line (3) is operated as an incoming call only line, the current detection circuit (75) and the call notification circuit (76) can be omitted. The effect of the present invention does not change.

The resistance values of the resistors (R ₇₁ ), (R ₇₂ ) and (R ₇₃ ) in the power supply polarity detection circuit (73) and the allowable resistance value for the line resistance (R _L ) are limited to those shown in the figure. This is not done, and many other modifications are considered, but the effect of the present invention does not change in any case.

[0084]

As described above, according to the present invention, in the above-mentioned subscriber line communication system, the home line terminal is supplied with required DC power from local power supply means inserted at a connection point with the subscriber line. Therefore, regardless of the line resistance of the subscriber line, the necessary and sufficient DC power can always be supplied, and the DC power that can be transmitted from the intra-office line termination device to the subscriber line is not changed. It is possible to increase the allowable value of the line resistance of the line, and it is possible to accommodate the terminal equipment whose line resistance of the subscriber line exceeds the allowable value in the exchange by using the existing intra-office line termination device and home line termination device. The accommodation range of the device can be expanded.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 shows a subscriber line communication system according to an embodiment of the present invention.

FIG. 3 shows a local power supply circuit in FIG. 2;

FIG. 4 shows the DC power supply state in FIG. 2 (standby state)

FIG. 5 shows a DC power supply state (calling state) in FIG.

FIG. 6 shows the DC power supply state (incoming call state) in FIG.

FIG. 7 shows a conventional subscriber line communication system.

8 is an intra-office line termination device in FIG.

FIG. 9 is a diagram of an in-home line termination device in FIG.

FIG. 10 shows the state of DC power supply in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 exchange 2 terminal device 3 subscriber line 4 local line termination device 5 home line termination device 6 terminal line 7 local power supply circuit 41 AC signal transmission / reception circuit 42, 72 power supply circuit 43, 75, 731, 732 current detection circuit 44 power supply polarity control Circuits 45, 51, 71 AC / DC separation circuit 52 Subscriber line interface circuit 53 Terminal interface circuit 54 Standby circuit 55 Call detection circuit 56 DC conversion circuit 73 DC termination circuit 74 Power supply polarity relay circuit 76 Call notification circuit 600 Local power supply means 601 AC / DC separation means 602 Power supply means 603 DC termination means 604 Power supply state control means 605 Terminal call detection means 606 Call state transfer means 741, 744, 761 Control sections 742, 743, 745, 746, 762 Connection section

Continuation of the front page (72) Inventor ▲ Taka ▼ Akihiko 2-3-9 Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Fujitsu Digital Technology Co., Ltd. In-house (72) Minoru Hirahara 4 Kamikadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Fujitsu Limited (72) Inventor Kazunori Mutsuyasu 4-1-1 Kamikadanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (4)

[Claims] 1. An end of a metallic two-wire subscriber line is connected to an exchange via an intra-office line termination device, and a terminal device is connected to the other end of the subscriber line via a home line termination device. The local line terminal has a function of supplying predetermined DC power to the home line terminal via the subscriber line, and the home line terminal is provided with a DC power supplied via the subscriber line. Along with having a function of receiving and operating power, the intra-office line termination device and the home line termination device, in a subscriber line communication system that exchanges an AC signal in a predetermined frequency band via the subscriber line, A power supply unit for supplying DC power necessary for the operation of the home line termination device to a connection point between the subscriber line and the home line termination device; and from the office line termination device via the subscriber line. The supplied DC power is DC termination means for terminating the subscriber line with a resistance lower than the terminating resistance of the subscriber line, and transmission / reception via the subscriber line between the local station terminal and the subscriber line terminal. The AC signal is prevented from being transmitted to the power supply means and the DC termination means, and the DC power supplied from the intra-office line termination device via the subscriber line is used for subscribing the home-line termination device. To prevent the power from being transmitted to the subscriber line connection terminal and transmit the DC power to the DC termination means, and to prevent the DC power supplied from the power supply means to the home line termination device from being transmitted to the subscriber line. A local power supply system comprising: a local power supply unit having an AC / DC separation unit. 2. The DC termination means according to claim 1, wherein said built-in power supply polarity identification function identifies that the polarity of said DC power supplied from said intra-office line termination device via said subscriber line has been inverted. 2. The local power supply system according to claim 1, wherein the termination resistance value is changed between a non-inversion state and an inversion state. 3. The DC termination means includes a power supply polarity identification function for identifying the polarity of the DC power supplied via the subscriber line from the intra-office line termination device, A power supply state control unit that controls the polarity of the DC power supplied from the power supply unit to the subscriber line connection terminal of the home line termination device based on the voltage polarity of the DC power identified by the power supply polarity identification function. The local power supply system according to claim 1, wherein the local power supply system is provided. 4. A terminal call originating means for monitoring a direct current supplied from said power supply means to said home terminal unit and detecting a call from said terminal device accommodated in said home terminal unit. Detecting means for terminating DC power supplied from the intra-office line terminating device via the subscriber line by the DC terminating means when the terminal call detecting means detects a call from the accommodation terminal device; 2. The local power supply system according to claim 1, further comprising a call state transfer means for changing a resistance value.