JPH06244936A - Emergency changeover system - Google Patents

Abstract

PURPOSE:To prevent interruption of talking from a trunk line to a telephone set at the time of restoration from a fault by throwing a contact from the position of an exchange into the position of the telephone set based on a non-switching signal from a controller and giving a changeover permission signal to an emergency switching control circuit after no telephone current flows at the time of the restoration. CONSTITUTION:When system-down or a fault takes place in the normal operation, an emergency switching signal is supplied to a relay RL, the excitation of the relay RE is released and common contacts of switches SW1, SW2 are thrown to the position of (b). Thus, a trunk line forms a loop with the telephone set to make talking with the telephone set 5 thereby keeping talking even on the occurrence of a fault. When a main power supply is stopped, since the relay RL is not excited, the common contacts of switches SW1, SW2 are thrown to the position of (b) and talking is made between the trunk line and the telephone set 5. When the system-down is released and even when an emergency switching signal is set, the talking is continued. When the talking is finished, the relay RL is excited by a control signal of the controller 6 and the common contacts of switches SW1, SW2 are thrown to the position of (b) and the normal operation is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emergency switching system in a private branch exchange such as a PBX.

[0002]

2. Description of the Related Art In a general private branch exchange or the like, when a serious failure such as system down / main power stop occurs, the office line is forcibly switched to the main telephone side. Secure a call with.

FIG. 3 is a block diagram showing a configuration example of a conventional system. The office line is connected to the switch SW1, and the switch SW1 is connected to the office line trunk (CBT) 1 having an interface function between the office line and the exchange. The plurality of office line trunks 1 are connected to an exchange (NW) 2.

Reference numeral 3 is a plurality of subscriber circuits (LC) connected to the exchange 2, and 4 is a telephone connected to these subscriber circuits 3. One of the subscriber circuits 3 is folded back and connected to the switch SW2. The switch SW2 is connected to the telephone 5. The main telephone 5 is used for talking with a central line when a serious failure occurs.

Reference numeral 6 is a control device (CC) for performing switching control of the exchange 2 and other control, and SW3 is a switch for giving an emergency switching signal to the control device 6 from the outside. RL
Is a relay whose one end is connected to -48V. The relay RL is adapted to be turned on / off by an emergency switching signal. Then, the above-mentioned switches SW1 and SW
2 is provided as a contact of this relay RL. Emergency switch circuit 1 with switches SW1 and SW2 and relay RL
Configures 0. The operation of the system configured as described above will be described below. (Normal operation) During normal operation, the relay RL is always on and the common contact of the switches SW1 and SW2 is a.
It is connected to the contact side. As a result, the central office line is connected to the telephone set 4 via the exchange 2. (At the time of failure) When a serious failure such as system down / main power stop occurs, or when an emergency switching signal is forcibly input from the switch SW3, the control device 6 sends an emergency switching signal (open signal) to the relay RL. Is applied to cancel the excitation of the exciting coil. As a result, the switches SW1 and SW2 are switched from the a-contact to the b-contact side. As a result, as is apparent from the figure, the central office line is folded back in front of the exchange 2 and connected to the telephone set 5. In this way, the call is maintained when a failure occurs. (At the time of recovery from failure) When the above-mentioned failure is recovered, the control device 6 turns on the emergency switching signal. As a result, the exciting coil of the relay RL is excited. Therefore, the switch SW
The common contact of 1 and SW2 is again connected to the a-contact side, and is in the normal connection state.

[0006]

In the conventional system described above, the common contact of the switches SW1 and SW2 is switched from b to a in the telephone 5 at the time of recovery from the emergency switching, so the call in progress is forcibly forced. There is a problem of being disconnected. In order to eliminate such defects,
There is a method in which a call is monitored by a call current or the like, and recovery from emergency switching is performed after the call ends. However, even if such a method is used, if the failure is the stop of the main power supply, the call current monitoring circuit cannot operate. Therefore, when the main power is turned on, the emergency switching circuit 10 is forced to operate even during a call. However, there is a problem that the call in progress is forcibly disconnected because the call is restored.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an emergency switching system which does not disconnect the call between the central office line and the main telephone at the time of recovery from a failure. .

[0008]

FIG. 1 is a block diagram showing the principle of the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals. The system shown in the figure is used when a serious failure such as system down / main power stop occurs in a digital exchange.
Emergency switching circuit 2 forcibly switching the central office line to the telephone 5
An emergency switching system with 0 is configured. In the figure, reference numeral 20 denotes an emergency switching circuit for forcibly switching the office line to the main telephone 5 side when a serious failure such as a system down / main power stop occurs.

In the emergency switching circuit 20, SW1 is a switch provided between the office line and the office line trunk 1, and S1 is a switch.
W2 is a switch provided between the telephone 5 and the subscriber circuit 3. Reference numeral 21 is a call monitoring circuit for monitoring a call current provided between the b contact of the switch SW1 and the b contact of the switch SW2, that is, in a loop from the office line to the telephone 5.

RL is a contact switching relay, 22 is a timer circuit which operates after a lapse of a certain period of time after power is turned on, and 23 is an emergency control for turning on / off the relay RL based on control signals from the call monitoring circuit 21 and the timer circuit 22. It is a switching control circuit.

Reference numeral 2 denotes an exchange connected to the trunk line trunk 1 and the subscriber circuit 3, and the switching of the exchange 2 is controlled by a control device 6. The control device 6 detects a system down or the like and notifies the relay RL of the emergency switching signal.

[0012]

It is assumed that the common contacts of the switches SW1 and SW2 are both connected to the side b by emergency switching and the office line is connected to the telephone 5. In this state, the telephone 5 is talking with the central office side. When the fault is the system down and the state is released, the control device 6 turns on the emergency switching signal given to the emergency switching circuit 20.

The emergency switching control circuit 23 is provided with a control signal from the call monitoring circuit 21. Even if the emergency switching signal is turned on, as long as the call monitoring circuit 21 recognizes a call, the relay RL is Does not turn on. Call monitoring circuit 21
Detects the end of the call and notifies the switching permission signal to that effect to the emergency switching control circuit 23, and the relay RL is turned on for the first time, and the switches SW1 and SW2 are connected to the exchange 2 side.

When the failure is the stop of the main power supply, when the state is released and the main power supply is restored and turned on, the timer circuit 22 counts for a fixed time, and after a fixed time, the emergency switching control circuit 23 is commanded to operate. give. As a result, if the call is ended by the control signal from the call monitoring circuit 21, the emergency switching control circuit 23 turns on the relay RL, and the switches SW1 and SW2 are connected to the exchange 2 side. As described above, according to the present invention, in any case, the call between the main telephone 5 and the central line is not disconnected at the time of recovery from the failure.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 is a circuit diagram showing a main part of an embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals. The office line and the signal line on the main telephone 5 side are actually composed of two lines as shown in the figure, and the switch SW shown in FIG.
1 and SW2 are two switches SW1A and SW1 respectively
B, SW2A, SW2B. The b contacts of the switches SW1A to SW2B are connected to the call monitoring circuit 21, respectively. The a-contact is connected to the exchange side.

The call monitoring circuit 21 comprises a diode bridge D1, D2, resistors R1, R2, a photodiode D3.
D4 and phototransistors Q1 and Q2. In the diode bridge D1, the common cathode connection point is connected to the resistor R1, and the other end of the resistor R1 is connected to the anode of the photodiode D3. The cathode of the photodiode D3 is connected to the common anode connection point of the diode bridge D1. This configuration is the same for the diode bridge D2 side. The phototransistors Q1 and Q2 are connected in series.

The timer circuit 22 is operated by the power supplies Vcc and VEE. The timer circuit 22 includes a resistor R
3, R4, R5, capacitors C1, C2, and mono-multivibrator U1. The series circuit of the resistor R3 and the capacitor C1 is connected between the power supplies Vcc and VEE, and the connection point of R3 and C1 is the mono-multivibrator U.
1 is connected to the A terminal. A protection diode D5 is connected in parallel with the resistor R3.

The resistor R4 and the capacitor C2 connected in series to it form a time constant circuit, and determine the output pulse width of the mono-multivibrator U1. The connection point between the resistor R4 and the capacitor C2 is connected to the T2 terminal of the mono multivibrator U1. The resistor R5 is connected to the collector of the phototransistor Q1, and the emitter of the phototransistor Q2 is connected to the power supply VEE.

The emergency switching control circuit 23 comprises a 3-input AND gate G1 and a transistor Q3 driven by the AND gate G1. The relay RL is connected as a collector load of the transistor Q3. An emergency switching signal is applied to the other end of the relay RL. This emergency switching signal is open when the emergency switching signal is input, and is ground potential in the normal state. The operation of the system configured as described above will be described below. (During normal operation) At this time, the emergency switching signal is on. Therefore, the relay RL is on and the exciting coil is excited. Therefore, the switches SW1 and SW2 are connected to the a-contact side, respectively, and are connected to the exchange 2 (see FIG. 1). Then, a call is made between the central office line and the telephone connected to the exchange 2. (At the time of failure) It is assumed that a failure such as system down or main power supply stop occurred during normal operation. When the system is down, the emergency switching signal is off (open) and the relay R
Given to L. Therefore, the excitation of the exciting coil of the relay RL is released, and as a result, the common contacts of the switches SW1 and SW2 are connected to the side b.

Therefore, the central office line forms a loop with the main telephone 5 to talk with the main telephone 5. In this way, the call can be maintained even when a failure occurs. Further, since the relay RL is not excited even when the main power supply is stopped, the common contact of the switches SW1 and SW2 is connected to the side b, and a call is made between the station line and the main telephone 5. (During failure recovery) System down is canceled and the emergency switching signal is turned on. However, when a call current flows in the call monitoring circuit 21, a current flows in the phototransistors Q1 and Q2, and the input of the AND gate G1 drops to "0" level. Therefore, AND gate G
The output of 1 becomes "0", the transistor Q3 cannot be driven, and the relay RL is not excited. As a result,
The common contacts of the switches SW1 and SW2 are still connected to the b contact, and the call continues.

Here, assuming that the call is completed, no current flows in the phototransistors Q1 and Q2,
The input of the AND gate G1 becomes "1". As a result, all three inputs of the AND gate G1 become "1", and the output becomes "1". Therefore, the transistor Q3 is turned on and drives the relay RL. The exciting coil is excited, the common contact of the switches SW1 and SW2 is connected to the a contact side, and normal operation is started.

Next, consider the case where the main power supply is restored from the stopped state. When the main power is turned on, the emergency switching signal turns on. However, the output of the mono-multivibrator U1, which is a timer circuit, becomes "1" after a lapse of a fixed time. Until then, the output maintains the "0" state. Therefore, the output of the AND gate G1 is "0",
Transistor Q3 does not turn on. As a result, the common contact of the switches SW1 and SW2 remains on the b side.

During this time, the call monitoring circuit 21 monitors the call current. When the output of the mono multivibrator U1 changes from the "0" state to the "1" state until then, if the call is continued, "0" is included in the input of the AND gate G1, and the output is "0". “It remains. Therefore, the transistor Q3 does not turn on and the station line and the main telephone 5
The call with is continued.

When the call ends and the call current stops flowing, all three inputs of the AND gate G1 become "1" and the transistor Q3 is turned on. As a result, the relay RL is excited, the common contact of the switches SW1 and SW2 is connected to the a side, and normal operation is started. in this way,
According to the present invention, the call is disconnected at the time of restoration from the fault because the station line and the exchange side are connected after confirming that the call between the station line and the main telephone 5 is finished at the time of restoration from the fault. Disappears.

In the above-described embodiments, the case where the mono-multivibrator is used as the timer circuit 22 is taken as an example. However, the present invention is not limited to this, and other types of timer circuits, such as a clock counter, may be used.

[0026]

As described above in detail, according to the present invention, it is possible to provide an emergency switching system which does not disconnect the call between the central office line and the main telephone at the time of recovery from a failure, and in practical use. Is very effective.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a main part of an embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration example of a conventional system.

[Explanation of symbols]

 1 office line trunk 2 switch 3 subscriber circuit 5 main telephone 6 control device 20 emergency switching circuit 21 call monitoring circuit 22 timer circuit 23 emergency switching control circuit RL relay SW1, SW2 switch

Claims (4)

[Claims] 1. An emergency switching system provided with an emergency switching circuit (20) for forcibly switching the office line to the main telephone (5) side when a serious failure such as system down / main power stop occurs in a digital exchange. The emergency switching circuit (20) includes a call monitoring circuit (21) provided in a loop from the office line to the main telephone (5) for detecting a call current, a relay (RL) for switching contacts, and a power supply. Timer circuit (22) that operates after a certain period of time after turning on
And an emergency switching control circuit (23) for performing on / off control of the relay (RL) based on control signals from the call monitoring circuit (21) and the timer circuit (22). . 2. The relay (RL) is configured such that its contacts are connected to the exchange (2) side or the main telephone set (5) side, and the relay (RL) is activated by an emergency switching signal from a control device (6). The emergency switching system according to claim 1, characterized in that the contact point is switched from the exchange (2) side to the telephone set (5) side. 3. Upon recovery from emergency switching, the call monitoring circuit (21) monitors the call current, and after the call current stops flowing, a switch permission signal is sent to the emergency switching control circuit (23). The emergency switching system according to claim 1, wherein the emergency switching system is provided. 4. When the failure is a stop of the main power supply, the timer circuit (22) is configured to give an operation signal to the emergency switching control circuit (23) after a lapse of a predetermined time when the emergency switching is restored. The emergency switching system according to claim 1, wherein: