JP2852209B2 - Power off notification circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power-off notification circuit, and more particularly to a terminal device (DT) in a data transmission system.
E) and a power termination notification circuit between the data termination device (DCE).

[0002]

2. Description of the Related Art Conventionally, a power-off notification circuit of this type has been used in a data transmission apparatus in a state where power is not supplied, for example, when the power is turned off because the power is turned off because the apparatus is not used and communication is started. Although it is not possible, it is necessary for the opposing device to determine whether the cause is a power loss of the opposing device or a failure of the line itself. In such a case, a power-off notification circuit is used.

As this power-off notification circuit, there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 63-7056. FIG. 3 is a block diagram of this conventional example. In FIG. 3, line terminators (DCE) 7 and 8 in the terminal device face each other via a data line. FIG. 3 shows a case where the DCE 7 detects a power-off on the DCE 8 side. The DCE 8 generates a power-off signal by a power-off detector (DET) 81 for detecting the power-off and this detection signal. Driver circuit (DR
V) and a power-down signal generation circuit (GEN) 82 for transmitting the signal to the uplink via the power-off signal 84. On the other hand, the DCE 7 is a power-down signal reception detection circuit (D
ET) 71, where the power cut-off on the DCE 8 side is detected.

Further, a power-off signal on the DCE8 side is transmitted to the DCE7.
As a method of transmitting to the side, each relay wire 74, 75, 85,
There is also a method in which a line 86 with a neutral point is used, and a direct current signal is transmitted using the double line.

[0005]

As described above, the conventional power-off notifying circuit detects a power-off and converts it into an AC power-off signal in order to transmit the detected power-off to a device of the opposite central station or another station. , Or need to prepare a heavy credit line.
Therefore, there is a problem that the circuit becomes complicated and the cost increases.

[0006]

A power-off notifying circuit according to the present invention includes a circuit for detecting a power-off in a data termination device, and a make contact which is operated by a detection signal of the power-off detecting circuit and connects to a terminal device. And a detection circuit for detecting a DC closed-loop signal that is completed when the relay operates between the two lines of the line in the terminal device. ing.

A relay connected between two lines of a line connected to the terminal device side and having a break contact which operates when the device is turned on and is restored when the power is turned off, in the data terminal device, and the line in the terminal device. And a detection circuit for detecting a DC closed loop signal generated when the relay circuit is restored between the two lines.

Further, a diode is inserted in series with a make contact or a break contact of the relay, and a detection circuit in the terminal device detects a one-way closed loop signal generated when the relay operates or recovers. It may be a circuit.

[0009]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a block diagram showing an embodiment.

In the figure, a data termination unit (DCE) 2
The terminal equipment (DTE) 1 is usually installed in the same station, and the distance between them is about 1 km even at a long distance, and the two equipments are connected by a four-wire type uplink line 3 and a downlink line 4. In this case, the DCE 2 is notified to the DTE 1 that the power is off.

The DCE 2 monitors a receiver circuit (REV) 23 for receiving a data signal, a driver circuit (DRV) 24 for transmitting a data signal, and a power supply voltage, and detects a power supply cutoff (PWR DET). 21 and a make contact 2 for short-circuiting between the two lines by the detection signal.
2a.

The DTE 1 detects a driver circuit (DRV) 12 for transmitting a data signal, a receiver circuit (REV) 13 for receiving a data signal, and a closed loop signal when the power supply is cut off on the DCE 2 side and the relay contact 22a is closed. , A closed-loop signal detection circuit 11 comprising a current detection power supply 111, a current detection circuit 112, and a high-impedance resistor 113.

When the power cut is detected by the DCE2, the two lines are short-circuited by the relay contact 22a, and the closed-loop signal is transmitted to the closed-loop signal detection circuit 1 on the DTE1 side.
In step 1, power failure is notified. Between the two lines that are short-circuited at the contact 22a, if each circuit does not form a DC loop due to insertion of a relay ring or the like, the two lines of the upstream line 3 (or the downstream line 4) indicated by the solid line a However, if this DC lube is formed, the two lines between the two lines indicated by the dotted line b are short-circuited. In this case DTE1
The side is also connected by the dotted line b.

FIG. 2 is a block diagram showing another embodiment. The difference from FIG. 1 is that a diode is inserted in series at a contact for short-circuiting between two wires, and power-off is notified by a one-way closed-loop signal. This makes it possible to identify the power failure notification signal when the line failure is a short-circuit failure. However, most of the normal line faults are open faults, and the method of FIG. 2 is used when more accurate power-off notification is required.

Referring to FIG. 2, only the difference from FIG. 1 will be described. When the power is cut off by the DCE 6, the relay 62 is operated, the contact 62 is closed, and a one-way closed loop signal is transmitted to the DTE 5 through the diode 64. Conveyed to the side. DTE5
The one-way closed-loop detection circuit 51 detects a one-way closed-loop signal by switching the DC power supply for detection of both polarities. If the line fault is a short-circuit fault, a closed-loop signal in both directions is detected, so that it is possible to identify this.

In FIGS. 1 and 2, when it is not particularly necessary to detect the power-off with high precision, the PWR D of the DCEs 2, 6 is used.
The TEs 21 and 61 are unnecessary, and the relays 22 and 62 may always be operated directly with the power supply voltage, and a contact that closes when the power supply is cut off may be used. That is, in this case, a break contact is used as the relay contact. Further, in this case, PWR D which requires a separate power supply to continue power supply even when the power is cut off
Since no ET is required, a separate power supply is not required and the circuit is extremely simplified.

[0017]

As described above, the power-off notification circuit of the present invention uses this closed-loop signal by short-circuiting between two lines as a method of notifying the power-off, so that the circuit is simple and reliable. This has the effect of notifying that the power has been turned off. In addition, there is an effect that a separate power supply is not required to detect a power-off.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional example.

[Description of Signs] 1 Terminal equipment (DTE) 2 Data termination equipment (DCE) 3 Uplink 4 Downlink 11 Closed loop detection circuit 12, 21, 52, 64 Driver circuit 13, 23, 53, 63 Receiver circuit 21, 61 Power supply Disconnection detection circuit (PWR DET) 22, 62 Relay 22a, 62a Relay contact 51 One-way closed loop detection circuit 64 Diode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-7056 (JP, A) JP-A-1-126605 (JP, A) JP-A-4-6932 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H04L 29/00

Claims (2)

(57) [Claims] 1. A circuit for detecting a power-off in a data termination device, and a diode operated between the two lines of a line operated by a detection signal of the power-supply detection circuit and having a make contact connected to a terminal device side.
And a relay that is connected via
A detection circuit for detecting a directional DC closed-loop signal generated when the relay operates between the two lines of the line in the terminal device. 2. A relay in which a break contact which operates when the power of the device is turned on and is restored when the power is turned off is connected via a diode between two lines of a line connected to the terminal device side in the data terminal device; And a detection circuit for detecting a directional DC closed loop signal generated when the relay circuit is restored between the two lines of the line.