JPH0983604A - Power cut notifying circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a circuit and to make transmission sure by using between a close loop signal shorting a spines as a method for notifying the power cut of a data terminal equipment-side of a terminal equipment-side. SOLUTION: When a DCE 2-side detects power cut by PWR DET 21, a relay 22 operates and a contact point 22a is closed, and the space (solid line a) between the two lines is shorted. The close loop detection circuit 11 of DTE 1 detects the close loop signal. A space (dotted line b) between the two up/down lines will do for the space between the two lines. When the relay 22 is always directly operated at power voltage without using PWR DET 21 and the contact point 22a is set to be a break contact point, the circuit is more simplified and different power supply is not required.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, this kind of power cutoff notification circuit is used in a data transmission device in a state where power is not supplied, for example, communication is performed when an opposite device is activated while the power is cut off because it is not used. However, it is necessary for the opposite device to determine whether the cause is a power cut of the partner device or a failure of the line itself. In such a case, the power cut notification circuit is used.

An example of this power-off notification circuit is shown in Japanese Patent 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 are opposed to each other via a data line. FIG. 3 shows a case where the DCE 7 detects a power failure on the DCE 8 side. The DCE 8 generates a power failure signal (DET) 81 for detecting a power failure and a power failure signal by this detection signal. Driver circuit (DR
V) 84 and a power cutoff signal generation circuit (GEN) 82 for sending to the uplink, while the DCE 7 receives a power cutoff signal reception detection circuit (D) for receiving the power cutoff signal of the uplink.
ET) 71, which detects a power failure on the DCE 8 side.

Further, the power-off signal on the DCE8 side is sent to the DCE7.
As a method of transmitting to the side, each relay line wheel 74, 75, 85,
There is also a method of transmitting a direct current signal by using a line with neutral point for 86 and utilizing this duplex line.

[0005]

As described above, the conventional power-off notification circuit detects a power-off and converts it into an AC power-off signal for transmission to the device of the opposite central station or another station. Or, it is necessary to prepare a duplex line.
Therefore, there is a problem that the circuit becomes complicated and the cost becomes high.

[0006]

A power-off notification circuit of the present invention includes a circuit for detecting power-off in a data terminating device, and a make contact which operates by a detection signal of the power-off detection circuit to connect to a terminal device side. And a detection circuit for detecting a DC closed loop signal completed when the relay operates between the two lines of the line in the terminal device. ing.

Further, a relay having a break contact which is operated by turning on the power supply of the device in the data terminating device and which is restored by cutting off the power supply is connected between two lines of the line connecting with the terminal device side, and the line in the terminal device. A detection circuit for detecting a DC closed loop signal generated when the relay circuit is restored may be provided between the two lines.

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

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, referring to FIG.
This will be described with reference to FIG. FIG. 1 is a block diagram showing an embodiment.

In the figure, a data terminating device (DCE) 2
The terminal device (DTE) 1 and the terminal device (DTE) 1 are usually installed in the same station, and the distance between them is about 1 km even at a long distance, and the two devices are connected by a 4-wire up-link 3 and down-link 4. In this case, the DTE1 side is notified of the power cutoff on the DCE2 side.

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 that short-circuits two lines of the line by this detection signal
And a relay 22 having 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 relay contact 22a is closed due to power failure on the DCE 2 side. The detection DC power supply 111, the current detection circuit 112, and the closed-loop signal detection circuit 11 including the high-impedance resistor 113 are provided.

When the DCE2 detects a power failure, the two lines of the line are short-circuited by the relay contact 22a, and the closed loop signal is sent to the closed loop signal detection circuit 1 on the DTE1 side.
It is detected in 1 and the power cut is notified. Between the two lines short-circuited at the contact 22a, if each line does not form a DC loop due to insertion of a relay loop or the like, the two lines of the up line 3 (or down line 4) shown by the solid line a If the DC lube is constructed, 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 to a contact that short-circuits two lines and a power cut is notified by a closed loop signal in one direction. In this case, when the line fault is a short-circuit fault, it can be distinguished from the power-off notification signal. However, most of the normal line failures are open failures, and the method of FIG. 2 is used when more accurate power-off notification is required.

In FIG. 2, only the difference from FIG. 1 will be described. When the DCE 6 detects a power failure, the relay 62 operates, its contact 62 is closed, and a unidirectional closed loop signal is transmitted via the diode 64 to the DTE5. It is transmitted to the side. DTE5
The unidirectional closed loop detection circuit 51 detects the unidirectional closed loop signal by switching the bipolar DC power supply for detection. When the line fault is a short-circuit fault, a closed loop signal in both directions is detected, so that it can be distinguished from this.

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

[0017]

As described above, since the power-off notification circuit of the present invention uses this closed loop signal by short-circuiting two lines of the line as a method of notifying the power-off, the circuit is simple and reliable. It has the effect of being able to notify the power failure. Further, there is an effect that a separate power source is not required to detect the power failure.

[Brief description of drawings]

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

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

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

[Explanation of symbols]

 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 Failure Detection Circuit (PWR) DET) 22,62 Relay 22a, 62a Relay contact 51 Unidirectional closed loop detection circuit 64 Diode

Claims (3)

[Claims] 1. A circuit for detecting a power failure in a data terminating device, and a make contact which is operated by a detection signal of the power failure detecting circuit and is connected between two lines connected to the terminal device side to short-circuit the two. And a detection circuit for detecting a DC closed loop signal generated when the relay operates between 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 recovers when the power is turned off is connected between two lines of a line connected to the terminal device side in the data terminating device, and the line in the terminal device. And a detection circuit for detecting a DC closed loop signal produced when the relay circuit is restored between the two lines. 3. A detection circuit in which 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 unidirectional closed loop signal generated when the relay operates or is restored. 3. The power cutoff notification circuit according to claim 1, wherein the power cutoff notification circuit is a circuit.