JPH08102803A - Communication equipment - Google Patents

Abstract

PURPOSE: To realize a stable operation even after a feeding switch is changed over by generating a set signal in accordance with the switch operation of a circuit power source and resetting a centeral arithmetic unit. CONSTITUTION: A change-over switch 11 is provided with the switches 11a and 11b of two circuits, which can simultaneously be changed over. The switch 11a selectively changes over a station power source from a line and a commercial power source from an AC adapter and outputs the signal to the circuit power source. A pull-up resistor 12 is connected to the switch 11b, and a pulse signal is generated to a point A when the switch 11b is changed over. A monostable multi-vibrator 13 outputs the pulse signal with the pulse signal as a trigger. A NOR circuit 15 generates the reset signal when the pulse signal is outputted from the monostable multi-vibrator 13 and adds the reset signal to the central arithmetic unit (control CPU).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device for switching between a station power source and a commercial power source for use, and more particularly to a communication device improved to prevent malfunction of a control CPU (central processing unit) at the time of power source switching.

[0002]

BACKGROUND OF THE INVENTION Generally, a central office or private branch exchange (PBX).
The communication device connected to the power supply unit via the line is configured to operate by inputting the power supply from the station or the power supply from the PBX (these power sources are referred to in this specification) via the line. . However, when the line distance is long, the loop resistance may cause a voltage drop of the local power supply voltage, and a sufficient voltage for operating the device may not be obtained.

Therefore, conventionally, an AC adapter or the like is used to provide another power supply for supplying power from a commercial power supply (local power supply), and when the station power supply voltage drops, this local power supply is performed from the station power supply. It is configured to switch to the power supply of.

By the way, in the conventional apparatus, the power supply is switched by manually switching the power supply switch. Here, the power supply switch is a non-shorting type switch in order to prevent collision of both power supplies. Need to use. Therefore, at the time of switching, there is a problem that the power supply is momentarily opened and the voltage drops, and the power supply noise may cause the control CPU to malfunction.

In order to avoid this inconvenience, it is possible to use an IC for low voltage monitoring together. In this case, however, the IC for low voltage monitoring is used for instantaneous fluctuations such as chattering noise of the switch. There was a problem that it could not be handled by IC.

[0006]

As described above, in the conventional device, there is a problem that the control CPU may malfunction due to power supply noise generated when the power supply switch is switched.

Therefore, an object of the present invention is to provide a communication device which can perform stable operation even after the power feeding switch is switched.

[0008]

In order to achieve the above object, the present invention provides a communication device, which is fed with a station power supply and a commercial power supply and whose operation is controlled by a central processing unit,
First switching means for switching the station power supply and commercial power supply, second switching means operating in conjunction with the first switching means, and the central operation corresponding to the switching operation of the second switching means. Reset signal generating means for generating a reset signal for the device, and resetting the central processing unit based on the reset signal generated by the reset signal generating means.

[0009]

In the present invention, the second switching means interlocking with the first switching means for switching the station power supply and the commercial power supply is provided,
Corresponding to the switching operation of the second switching means, a reset signal is generated by the reset signal generating means, and the central processing unit of the device is reset by this reset signal.

As a result, stable operation can be performed even after switching between the station power supply and the commercial power supply.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a communication device according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a main part of a communication device according to the present invention.
A configuration is shown in which a station power supply from a line (not shown) and a commercial power supply from an AC adapter (not shown) are switched by a changeover switch 11 and the whole is output to a circuit power supply of a communication device (not shown).

In FIG. 1, the changeover switch 11 is provided with two circuits of switches 11a and 11b which can be changed over at the same time, and the switches 11a and 11b are each constituted by a non-shorting type switch. Here, each of the switches 11a and 11b has time to be open when the switches are switched.

The switch 11a is connected to the station power source and A
A commercial power source from the C adapter is added, and the station power source from the line and the commercial power source from the AC adapter are selectively switched and output to a circuit power source (not shown).

A pull-up resistor 12 is connected to the switch 11b, and when the switch 11b is switched, a pulse signal which falls from a high level to a low level is generated at a point A. The pulse signal generated at the point A is applied to the monostable multivibrator 13.

Monostable multivibrator 13
Outputs a pulse signal that is at a high level for a predetermined period triggered by the falling edge of the pulse signal generated at point A. Further, the low voltage detection circuit 14 monitors the circuit voltage and outputs a pulse signal which is at a high level for a predetermined period when the circuit voltage falls below a predetermined voltage set in advance.

The pulse signal output from the monostable multivibrator 13 and the pulse signal output from the low voltage detection circuit 14 are applied to the NOR circuit 15.

The NOR circuit 15 generates a reset signal when a pulse signal is output from the monostable multivibrator 13 or when a pulse signal is output from the low voltage detection circuit 14, and the reset signal is not shown in its entirety. It is added to the reset terminal of the central processing unit (control CPU) of the communication device.

The detailed operation of the circuit shown in FIG. 1 will be further described with reference to FIGS.

FIG. 2 shows a change with time of the signal of each signal line when the changeover switch 11 is changed over.

When the selector switch 11 is switched from the line side to the AC adapter side or vice versa, the common terminals of the switches 11a and 11b are once opened and then connected to the opposite side. This period is the switch switching time shown in FIG. 2, that is, the time from the time point ta to the time point tb.

During this switch switching time, the circuit voltage gradually decreases and returns to the original voltage at time tb.

Further, the signal at the point A, which is the input to the monostable multivibrator 13, is at the GND level because it is connected to the ground (GND) at the time point ta. The monostable multivibrator 13 detects the falling edge of the signal at the point A and generates a pulse signal that is at high level for a predetermined period.

At the time point tb, the switch 11b is connected to the contact on the opposite side, so that the voltage is supplied to the point A by the pull-up resistor 12 and returns to the original voltage level again. However, the output of the monostable multivibrator 13 is
An arbitrary constant set in the monostable multivibrator 13 maintains the high level until time tc. That is, the monostable multivibrator 13 generates a pulse signal which rises in response to the operation of the changeover switch 11 and falls at the time point tc. The pulse signal output from the monostable multivibrator 13 is inverted by the NOR circuit 15 and becomes a reset signal.

In this case, since the circuit voltage does not drop to the detection level of the low voltage detection circuit 14, the low voltage detection circuit 14 does not operate.

FIG. 3 shows the time change of the signal of each signal line when the changeover switch 11 is changed over and the switch changeover time (ta-tb) is long.

When the changeover switch 11 is changed over, as shown in FIG.
As in the case of, the circuit voltage begins to drop. Then, at the time td, the low voltage detection circuit 14 operates, and the low voltage detection circuit 14 outputs a pulse signal that is at a high level for a predetermined period.

Here, at time tc, the output of the monostable multivibrator 13 is restored to the low level, but since the high voltage pulse signal is generated from the low voltage detection circuit 14, the NOR circuit 15 outputs the time te. The reset signal that goes to low level continues to be output.

Thus, the control CPU can be stably reset even when the switching time is long, and the communication device can be stably controlled.

FIG. 4 is a flow chart showing the operation of the embodiment shown in FIG. First, the operation of the changeover switch 11 is monitored (step 100), and when the changeover switch 11 is operated, an operation detection pulse (a pulse generated at the point A) is generated (step 110), and this is detected by the monostable multivibrator 13. To enter. As a result, a high-level pulse signal is output from the monostable multivibrator 13 (step 120). This high-level pulse signal is inverted by the NOR circuit 15 and becomes a low-level reset signal.

Next, it is checked whether or not the low voltage is detected by the low voltage detection circuit 14 (step 130). When the low voltage is detected here, the low voltage detection circuit 14 outputs a high level pulse signal. (Step 140). This high-level pulse signal is inverted by the NOR circuit 15 and becomes a low-level reset signal.

The low-level reset signal output from the NOR circuit 15 is applied to the control CPU, and the control CPU is reset by this reset signal.

When the low-level reset signal output from the NOR circuit 15 rises to the high level and the reset of the control CPU is released, the normal operation is started (step 150).

According to such a configuration, the control CPU does not malfunction due to the power supply noise generated when the power supply switch is switched, and the stable operation of the communication device is guaranteed.

In the embodiment shown in FIG. 1, the changeover switch 11 is configured so that only the positive power source side is changed over as shown in FIG. 5A.
As shown in (b), a three-circuit configuration may be adopted, and both positive and negative sides may be switched.

In addition, it is obvious that even if four or more switches are used, the same operation can be achieved.

In the embodiment shown in FIG. 1, the reset signal is generated by using the monostable multivibrator 13 as shown in FIG. 6 (a). As shown in b), instead of the monostable multivibrator 13, a counter 13 that starts a counting operation by an edge trigger of an input signal is used.
1 may be used to generate the reset signal.

Further, as shown in FIG.
Instead of the monostable multivibrator 13 shown in (a), a delay circuit 132 and an AND circuit 133 may be used to generate the reset signal.

In any case, it is obvious that the same operation as the embodiment shown in FIG. 1 can be performed.

In the above description, an example in which an AC adapter is used as the commercial power source has been shown, but it goes without saying that other power sources can also be used.

[0040]

As described above, according to the present invention, the control CPU is operated when the power feeding system is switched by the switch operation.
Is reset, there is an effect that a stable operation can be performed even after the switch operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of a communication device according to the present invention.

FIG. 2 is a signal waveform diagram showing a time change of a signal of each signal line when the changeover switch shown in FIG. 1 is changed.

FIG. 3 is another signal waveform diagram showing the time change of the signal of each signal line when the changeover switch shown in FIG. 1 is changed.

FIG. 4 is a flowchart showing an operation in the embodiment shown in FIG.

5 is a circuit diagram showing another configuration example of the changeover switch shown in FIG.

FIG. 6 is a circuit diagram showing another configuration of the reset signal generator shown in FIG.

[Explanation of symbols]

 11 changeover switch 11a, 11b switch 12 pull-up resistor 13 monostable multivibrator 14 low voltage detection circuit 15 NOR circuit

Claims (1)

[Claims] 1. A communication device, which is supplied with a station power supply and a commercial power supply and whose operation is controlled by a central processing unit, and a first switching means for switching between the station power supply and the commercial power supply, and interlocking with the first switching means. And a reset signal generating means for generating a reset signal to the central processing unit in response to the switching operation of the second switching means. The reset signal generating means generates the reset signal for the central processing unit. A resetting signal for resetting the central processing unit.