JPH0213879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a remote monitoring and control device.

[Background technology]

In some systems, such as supply and discharge pump control, two pumps are operated alternately in order to increase the reliability of supply and discharge equipment. In addition, in such automatic alternating operation, when an abnormal alarm signal such as a full liquid alarm is input, two motors are operated simultaneously, and the operation continues until the alarm signal or control signal is released. .

A conventional example of this type is shown in FIG. In other words, is the internal unit side of the control panel, and is the door side.
Dedicated lines _L1 to _L14 , which serve as crossover lines, are used to connect the two. A ₁ is a switch for "auto", "test", and "off"; A ₂ is a switch for "self-exchange" and "independent";
AR is an alternating switching device using an automatic alternating operation relay circuit, MC ₁ and MC ₂ are electromagnetic contactors, ALX ₁ and ALX ₂
is an alarm relay, th ₁ and th ₂ are thermal relay switching contacts, H is an indicator lamp group, and Y is a simultaneous drive relay. Switch changeover switch A ₁ to "Auto",
When the signal contact 1 that commands alternate operation turns on and off repeatedly while the changeover switch A ₂ is switched to "self-alternating", the alternate switching device AR operates each time, and the electromagnetic contactors MC ₁ and MC are switched on and off. Drive ₂ alternately,
As a result, two motors (not shown) are operated alternately. At the same time, the normally open contacts mc ₁ , mc ₂ of the electromagnetic contactors MC ₁ , MC ₂ are turned on, so depending on their operation, the stop indicator lamps RL ₁ , RL ₂ of the lamp group H are changed to the operation indicator lamps GL ₁ , GL _{2 .} can be switched to

Further, when full liquid is detected and the alarm contact 2 for instructing simultaneous operation is turned on, the simultaneous drive relay Y and alarm lamps H ₁ and H ₂ on the door side and external detection section are activated. Since the normally open contact _y1 is closed by the operation of the simultaneous drive relay Y, the electromagnetic contactors _MC1 and _MC2 operate simultaneously in response to any output signal of the alternating switching device AR, and simultaneous operation is performed. The normally open contact _y2 provides hysteresis to the simultaneous operation to prevent the simultaneous drive relay Y from chattering. Also, alx ₁ and alx ₂ are alarm relays ALX ₁ ,
ALX ₂ contacts, OL ₁ and OL ₂ are its alarm indicator lamps,
R and S are input terminals of the AC power supply.

However, this remote monitoring and control device requires 12n (dedicated lines) + ₂ (common lines) dedicated lines L1 to _L14 between the internal unit side and the door side of the control panel. Furthermore, when detecting and displaying the full and low liquid level, the number of dedicated lines increases, for example, 18n+2.
The drawback was that it required a book. n is the number when the same type of remote monitoring and control devices are installed on a common control panel. This also caused a problem in that it was difficult to open and close the door.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a remote monitoring and control device that can reduce the number of dedicated lines.

[Disclosure of the invention]

In the remote monitoring control device of the present invention, a common terminal is connected to one side potential of an AC power source based on a command signal for alternate operation transmitted through a command signal line, and a pair of switching contacts are connected each time the command signal is generated. an alternating switching device having a contact portion that alternately switches between the two, a pair of dedicated lines connected to the pair of switching contacts of the alternating switching device via a diode, and a potential on the other side of the pair of dedicated lines and the AC power supply. a pair of control relays connected between the diodes and the diodes through diodes in the same direction as the diodes and controlling the pair of loads in response to one-sided half-wave current passing through these diodes;
The control relays are connected between the other side potential and the pair of dedicated lines via a diode facing opposite to the diode, and are connected to the other side of the pair of dedicated lines in response to the operation of the load control system of the pair of control relays. an operating contact that conducts a side half-wave current; and a diode that is connected between the pair of dedicated lines and the one side potential through a diode in the same direction as the diode connected to the operating contact, and turns on the operating contact. a load monitoring control circuit having a display drive relay to which the other side half-wave current is energized; and a dedicated line other than the pair of dedicated lines, which are connected in parallel to each other so that only one of them operates. A pair of detection parts each having a pair of abnormality detection contacts, one of which is connected in series with a flicker contact, and connected between one side potential of the AC power source and the other dedicated line via diodes facing oppositely to each other. and a pair of receiving means connected between the other dedicated line and the other side potential of the AC power supply through diodes facing oppositely to each other, and output signals of the pair of receiving means are respectively inputted to each output. a first display unit having a pair of intermittent current discrimination circuits that discriminate between an intermittent state and a continuous state of a signal; and a pair of indicator lights that respectively respond to an intermittent discrimination output and a continuous discrimination output of one of the intermittent current discrimination circuits; a load abnormality display circuit having a second display section having an indicator light responsive to one of the other intermittent discrimination output and continuous discrimination output of the intermittent current discrimination circuit and a simultaneous drive control relay responsive to the other; simultaneous drive means having a contact connected between a pair of switching contacts of the alternating switching device of the load monitoring control circuit, responsive to the output of the simultaneous drive control relay, and stopping when the command signal disappears. .

According to the configuration of the present invention, in the load monitoring control circuit, the operation signal for operating the control relay and the display signal for operating the display drive relay are distinguished between one side half-wave current and the other side half-wave current. Since the data is transmitted through a common dedicated line, load monitoring control is possible with a small number of dedicated lines. In addition, since the load abnormality display circuit uses a common dedicated line to distinguish between half-wave current on one side and half-wave current on the other side, and distinguish between intermittent signals and continuous signals, load abnormality can be displayed with a small number of dedicated lines. control becomes possible, and the number of dedicated lines can be reduced for the entire remote monitoring and control device.

Further, since the simultaneous operation of the load monitoring control circuits is achieved by the simultaneous operation signals transmitted from the simultaneous operation control relay provided in the load abnormality display circuit, a dedicated line for the simultaneous operation signals is not required.

Further, since there is no possibility that the command signal for alternate operation and the simultaneous operation signal, which are particularly important, are mixed, safe operation reliability can be ensured against device failure.

A first embodiment of the invention is shown in FIGS. 2 to 6. That is, the configuration of this remote monitoring and control device will be explained along with its operation. ′ is the internal device of the control panel,
' is a door. First, in the load monitoring control circuit,
Changeover switches A ₃ and A ₄ to "automatic" and "self-transfer"
The command signal line is turned on by turning on external signal contact 1, which generates a command signal for alternate operation.
One half-wave current of the AC power supply serving as a command signal flows through L ₂₀ and diodes D ₁₄ and D ₁₅ to relay N ₁ , energizing relay N ₁ and closing its normally open contact n ₁ . Therefore, the normally open contact _n1 repeats on and off in response to the on and off of the signal contact 1. This normally open contact
When n ₁ is turned on, one side potential r connected to one terminal of the AC power supply → normally open contact n ₁ → changeover switch
A ₃ , A ₄ → Alternating switching device AR ₁ → A closed circuit with the other side potential s connected to the other terminal of the AC power supply is formed, and while an AC voltage is applied to the alternating switching device AR ₁ , the one side potential The common contact of contact section ry ₂ is connected to. This alternating switching device AR ₁ operates so that when signal contact 1 turns off, normally open contact n ₁ of relay N ₁ turns off and switching contact ry ₂ switches, so it switches every time signal contact 1 repeats on and off. contact ry ₂
is switched.

That is, the alternating switching device AR ₁ includes a diode bridge rectifier RC, a constant voltage diode ZD, a two-winding latching relay LR, a transistor Tr, diodes D ₁ to D ₅ , resistors R ₁ to _{R 3} , and capacitors C ₁ and C. It consists of ₂ . Now the switching contact ry ₁ of the latching relay LR is connected to the latching relay LR as shown in Figure 2.
When connected to the winding S side of the
The rectified voltage is applied to capacitor C ₁ through diodes D ₁ and D ₂ to charge it. While the signal contact 1 is on, the transistor Tr is off due to the voltage division setting of the resistor _R3 . When signal contact 1 is turned off in this state, the voltage division of resistor R ₃ disappears, so the charging current of capacitor C ₁ is transferred to the diode.
It flows from the emitter to the base through _D5 , turns on the transistor Tr, and discharges the capacitor _C1 . At this time, a discharge current flows through the winding S of the latching relay LR, which excites it, so the relay LR operates, and the switching contacts ry ₁ and ry ₂ are switched to the opposite side.
Retained. When signal contact 1 is turned on again, capacitor _C2 on the winding RS side is charged, and when signal contact 1 is turned off in the same way as above, winding RS
is energized, and the switching contacts ry ₁ and ry ₂ are switched and held at their original positions. In this way, the switching contacts ry ₁ and ry ₂ switch each time the signal contact 1 changes from on to off.

By the operation of this alternating switching device AR ₁ , the contact
When ry ₂ is switched to switching contact a side, diode D ₆ → Dedicated line L ₁₆ → Diode D ₇ → Resistor R ₄ → Control relay X ₁ → Normally closed contact of overcurrent alarm relay ALX ₃
alx ₃ → The circuit containing the other side potential s is closed, the half-wave current on one side of the AC power supply is energized, and the control relay X ₁
is activated and its normally open contact x ₁ closes and the magnetic contactor
MC ₁ is activated, and one motor M ₁ , which is a load, is operated. In this way, when the load control system enters the operating state, the normally open contact mc ₁ of the magnetic contactor MC _1, which is the operating contact that responds to the operation, closes, so the other side potential s → normally open contact mc ₁ → diode D ₁₀ → dedicated line
L ₁₆ -> Diode D ₁₁ -> Display driving relay Z ₁ -> Due to the closed circuit of the potential r on one side, a half-wave current on the other side of the AC power supply is energized, and the relay Z ₁ operates. Therefore, the switching contact _z1 of the relay _Z1 is switched, the display circuit 3 for the motor _M1 is operated, and the operation of the motor _M1 is displayed.

Similarly, when the contact part ry ₂ is switched to the switching contact b side by the switching operation of the alternating switching device AR ₁ , the diode D ₈ → dedicated line L ₁₅ → diode D ₉
→Resistor R ₅ →Control relay X ₂ →Overcurrent alarm relay
A one-sided half-wave current flows through the normally closed contact ALX ₄ of ALX ₄ , activating the control relay X ₂ , which activates the magnetic contactor.
MC ₂ is activated, and motor M ₂ , which is a load, is operated. Also, since the normally open contact MC ₂ of the magnetic contactor MC ₂ , which is the operating contact, is closed, the diode D ₁₂ → Dedicated line
L ₁₅ → Display drive relay Z ₂ through diode D ₁₃
A half-wave current is applied to the other side, and the switching contact _z2 is operated, so that the display circuit 4 for the motor _M2 changes from a stop display to an operation display. These display circuits 3 and 4
For example, it consists of a running lamp and a stop lamp. In this way, each time the signal contact 1 repeats the on/off operation, the motors M ₁ and M ₂ are operated alternately, and the display circuits 3 and 4 are operated correspondingly.
Note that C ₃ to C ₆ and C ₈ are capacitors for smoothing the half-wave current, RC ₁ is a rectifier for the display lamp, C ₇ is the smoothing capacitor, and L ₁₇ and L ₁₉ are common lines.

On the other hand, in the load abnormality display circuit, motor M ₁ ,
Water tank (tank) that is supplied and discharged by alternating operation of _M2
The liquid level state is detected by resistance changes between a plurality of electrode rods installed in the water tank, and is detected by a floatless relay K. This floatless relay K
The simultaneous drive control relay P of the liquid level display section 5 is activated by the full liquid abnormality signal detected by the sensor, and when the normally open contact p is closed, the normally open contact of the diode D ₁₆ → relay N _{1 is} activated.
n ₁ ′ (on state) → diode D ₁₇ activates simultaneous drive relay N ₂ which is a simultaneous drive means. And a simultaneous drive relay connected between switching contacts a and b
When the normally open contact N ₂ of N ₂ closes, the alternating switching device
Switching contacts a and b of contact part ry ₂ of AR ₁ are short-circuited, so while normally open contact _{n 1} ' is on, control relays X _{1 and} both operate, and the electromagnetic contactors MC ₁ and MC ₂ operate at the same time.Therefore, the motors M ₁ and M ₂ are operated at the same time, and the display circuits 3 and 4 display operation at the same time. Furthermore, by closing the normally open contact n ₂ ′ of the simultaneous drive relay N ₂ , the normally open contact p is self-held, and by closing the normally open contact n ₂ ″, the alarm indicator lamp OL lights up. On the other hand, simultaneous drive control By closing the normally open contact p of the relay P, the relay _N3 for transfer is energized through the diode D ₁₆ → command signal line L ₂₀ → diode D ₁₉ , and its contact drives the alarm lamp etc. outside the control panel.C ₁₀ is a smoothing capacitor.

When thermal relays TR ₁ and TR ₂ operate due to overcurrent during each operation of motors M ₁ and M ₂ , their switching contacts tr ₁ and tr ₂ switch, magnetic contactors MC ₁ and MC ₂ stop, and alarm relay ALX is activated. ₃ , ALX ₄ is activated.
The operation of these alarm relays ALX ₃ and ALX ₄ opens the normally closed contacts ALX ₃ and ALX ₄ , so the control relays X ₁ and
X ₂ is turned off, and alarm relays ALX ₃ and ALX ₄
When the normally open contacts alx′ ₃ and alx′ ₄ close, the display drive relays Z ₁ and Z ₂ flicker due to the operation of the flicker contact fcr of the flicker relay FCR.
The display circuits 3 and 4 perform a display operation by blinking. F
is a fuse, and R and S are 200V AC power supply terminals.

Incidentally, when the changeover switch _A3 is switched to "Test", the motors _M1 and _M2 can be operated alternately by going back and forth between "Test" and "Off", regardless of the signal at signal contact 1. In addition, changeover switch A ₄ is set to “self-transmission”.
If you switch to "single" instead of "single", the alternating switching device
Only one of motors M ₁ and M ₂ is operated regardless of AR ₁ .

Next, the above-mentioned floatless relay K and liquid level state display section 5 will be explained. That is,
As shown in Figure 3, detection electrode rods (not shown) are placed in a water receiving tank (not shown) and an elevated water tank (not shown) to detect resistance changes depending on the position of the liquid level between the electrode rods. Drive relay K.
And the abnormality detection contact Q ₁ of the floatless relay K,
Q ₃ detects the full water status of each tank, and abnormality detection contact Q ₂ ,
Q ₄ detects the state of water loss in each tank, and a flicker relay contact fcr ₁ is connected in series to the abnormality detection contacts Q ₂ and Q ₄ , and the flicker relay FCR ₁ is connected to an AC power source E.

In an elevated water tank, when the water tank is full, the abnormality detection contact Q ₁ closes, and an alternating current is generated through the diode D ₂₀ connected to the abnormality detection contact Q ₁ and the diode D ₂₂ connected in the same direction via the dedicated line L ₁₈ . A half-wave current on one side flows from the other side potential s of the power source E to the one side potential r, and the receiving relay _Z3 , which is a receiving means, operates continuously, and its contact point _z3 is turned on. In addition, when the water is low, the abnormality detection contact Q ₂ closes and the same one-sided half-wave current flows as described above, but since the flickering contact fcr ₁ is flickering, the receiving relay Z ₃ operates intermittently, Contact _z3 flickers.
In these cases, it is impossible for the same elevated water tank to be full of water and in an abnormal state at the same time.
Each abnormality detection contact Q ₁ , Q ₂ of floatless relay K
are never closed at the same time.

On the other hand, the detection operation of the water tank filling abnormality and water decreasing abnormality is performed by half-wave energization on the other side of the AC power source E via the dedicated line L ₁₈ by the diodes D ₂₁ and D ₂₃ . Therefore, the same operation as described above is performed independently without mutual interference with the operation signal of the elevated water tank. _CL1 ,
CL ₂ is a common line, C ₁₀ and C ₁₁ are smoothing capacitors,
B ₁ and B ₂ are terminals of the dedicated line L ₁₈ .

Now, when contacts z ₃ and z ₄ are closed in a continuous state, the first switch that displays full water in response to the continuous determination output, etc.
Indicator light KL ₁ of display unit U ₁ and second display unit U ₂
The simultaneous drive control relay P operates, and the contacts z ₃ and z ₄
When the is closed to an intermittent state due to flicker operation, the indicator light KL ₂ of the first display unit U ₁ and the indicator light KL ₄ of the second display unit U ₂ , which indicate water reduction, are lit in response to the intermittent judgment output. Intermittent current discrimination circuit
It is determined and driven by SP ₁ and SP ₂ . EE is a DC power supply that drives the intermittent current discrimination circuits SP ₁ and SP ₂ .

Next, the configuration and operation of the intermittent current discrimination circuit _SP2 will be explained based on FIGS. 4 to 6. 1
1 is an input interface circuit that converts the on/off state of contact z ₄ into high/low output voltage;
a, 11b, resistors R ₁₂ and R ₁₃ for chattering removal and smoothing, and capacitor C ₁₃ , and generates voltages as shown in Fig. 6A in response to the normal period, full water signal input period, and low water signal input period. do. 12 is a retrigger type monostable multivibrator that is triggered by the rise of the output voltage of the input interface circuit 11. The output pulse width is set by an external resistor R ₁₄ , a variable resistor R ₁₅ and a capacitor C ₁₄ . As shown in FIG. 6B, the output terminal (Q) is at a high level for a certain period of time immediately after the input of the full water signal and during the input period of the low water signal. The reason why the level is high during the water reduction signal input period is because the monostable multivibrator 12 is triggered and enters a metastable state, but is retriggered before entering a stable state, and the on/off period of contact _z4 is equal to the monostable multivibrator 12. It needs to be shorter than the metastable period of the vibrator 12. 13 is an integrating circuit that integrates the output voltage of the monostable multivibrator 12, and a variable resistor for adjusting the charging speed.
It consists of _R16 , _R17 , a capacitor _C15 , a resistor _R18 for instantaneous discharge, and a diode _D6 , and its output voltage is as shown in Figure 6C, and during the signal input period, the pulse width of Figure 6B is Because it is narrow, when only one pulse is used, the threshold value V _TH is not exceeded, and as the water reduction signal is input, the normally open contact z ₄ operates intermittently, and when the pulse width in Figure 6B becomes longer, the output voltage exceeds the threshold value V _TH . It will be exceeded. 14 is a driver circuit that has a function of comparing the threshold value V _TH and the input voltage, and the inverter 1
4a, 14b, a transistor Tr ₁ and a base resistor R ₁₉ , and the voltage shown in FIG _.
6D, the output reaches a high level as shown in FIG. 6D, and the indicator light (yellow display) _KL4 on the second display unit _U2 is turned on to indicate the water loss. 15 is a signal inversion circuit that inverts the output of monostable multivibrator 12;
The inverting output terminal Q of No. 2 is used. 16 is the output of the input interface circuit 1 and the signal inversion circuit 15
This is an AND circuit that takes the logical value of the output of the diode
D ₁₇ , D ₁₈ and a resistor R ₂₀ , and as shown in FIG. ,
A simultaneous drive control relay P indicating the full water state of the second display unit U ₂ is operated via a driver circuit 17 consisting of a transistor Tr ₂ and a base resistor R ₂₁ . In addition, each indicator light KL ₄ consists of a light emitting diode LED ₁ and its current limiting resistor R ₂₃ , as shown in FIG. R ₂₆ is the output resistance of contact z ₄ .

According to this embodiment, in the load monitoring control circuit, the operation signal for operating the control relays X ₁ and X ₂ and the display signal for operating the display drive relays Z ₁ and Z ₂ are connected to one half-wave current. The number of dedicated lines is reduced because transmission is carried out using a common dedicated line to distinguish between the current and the other half-wave current.
Load monitoring control is possible with 4n+2 wires. Also,
In the case of the load abnormality display circuit, the dedicated line was used to distinguish between half-wave current on one side and half-wave current on the other side, and to distinguish between intermittent signals and continuous signals.
Up to four types of signal information can be displayed independently with one _L18 , and if there are n pieces of these four types of signal information, it will only be n times that number, so it is possible to display load abnormalities with a small number of dedicated lines. Since control is possible, the number of dedicated lines can be reduced for the entire remote monitoring and control device.

Further, since the simultaneous operation of the load monitoring control circuits is achieved by the simultaneous operation signals transmitted from the simultaneous operation control relay provided in the load abnormality display circuit, a dedicated line for the simultaneous operation signals is not required.

Further, since there is no possibility that the command signal for alternate operation and the simultaneous operation signal, which are particularly important, are mixed, safe operation reliability can be ensured against device failure.

In the above embodiment, the flickering operation is performed when the water level is abnormally low, but the flickering operation may be performed when the water level is abnormally high.

In addition, Figures 4 to 6 show intermittent current discrimination circuits.
Although SP ₂ and the second display unit U ₂ have been explained,
The same applies to the intermittent current discrimination circuit SP ₁ and the first display unit U ₁ .

Further, as a modified example of the receiving means, receiving relay Z ₃ ,
A photocoupler may be used instead of _Z4 .

A second embodiment of the invention is shown in FIG. That is, this remote monitoring and control device connects the simultaneous drive relay N ₄ in series to the normally open contact p of the simultaneous drive control relay P and connects it to an AC power supply, and also connects the simultaneous drive relay N 4 to the self-holding contact p of the simultaneous drive control relay N ₄ . Connect n ₄ ' in series with signal contact 1 to form signal contact 1 and self-holding contact.
A series circuit of n ₄ ' is configured to be connected in parallel to the normally open contact p. The operation of simultaneous drive control relay P turns on its normally open contact p, so simultaneous drive relay N ₄ operates, and its contact n ₄ closes to simultaneously drive control relays X ₁ and X ₂ . Also, the normally open contact n ₄ ″ closes and lights up the alarm indicator lamp OL.

This embodiment has an advantage over the first embodiment in that relays N ₁ and N ₂ can be omitted except that the transfer contacts cannot be taken out. The rest is the same as the first embodiment.

〔Effect of the invention〕

According to the remote monitoring control device of the present invention, in the load monitoring control circuit, the operation signal for operating the control relay and the display signal for operating the display drive relay are divided into half-wave current on one side and half-wave current on the other side. Since transmission is carried out using a common dedicated line, load monitoring and control can be performed with a small number of dedicated lines. In addition, since the load abnormality display circuit uses a common dedicated line to distinguish between half-wave current on one side and half-wave current on the other side, and between intermittent signals and continuous signals, load abnormality can be displayed with a small number of dedicated lines. control becomes possible, and the number of dedicated lines can be reduced for the entire remote monitoring and control device.

In addition, since the simultaneous operation of the load monitoring control circuit is achieved by the simultaneous operation signal transmitted from the simultaneous operation control relay provided in the load abnormality display circuit, a dedicated line for the simultaneous operation signal is not required, and
Since there is no risk of mixing with the command signal for alternate operation, which is particularly important, there is an effect that safe operation reliability can be ensured against device failure.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional example, Fig. 2 is a circuit diagram of a first embodiment of the present invention, Fig. 3 is a circuit diagram of a liquid level detection circuit, and Fig. 4 is a block diagram of an intermittent current discrimination circuit. 5 is a circuit diagram thereof, FIG. 6 is a time chart thereof, and FIG. 7 is a circuit diagram of a second embodiment. L ₂₀ ...Command signal line, 1...Signal contact that outputs the command signal, r...One side potential of AC power supply, s...
...Other side potential, AR ₁ ...Alternating switching device, ry ₂ ...
Contact parts, a, b...Switching contacts, _L15 , _L16 ...Pair of dedicated lines, _L18 ...Another dedicated line, _D6 ~ _D13 , _D20 ~
D ₂₃ ... Diode, X ₁ , X ₂ ... Control relay,
M ₁ , M ₂ ... Motor as load, mc ₁ , mc ₂ ...
Contacts that are operating contacts, Z ₁ , Z ₂ ... display drive relays, Z ₃ , Z ₄ ... reception relays of the receiving means, Q ₁ to _{Q 4}
...Abnormality detection contact, fcr ₁ ...Flicker contact, SP ₁ ,
SP ₂ ... Intermittent current discrimination circuit, T ₁ , T ₂ ... Detection section,
KL ₁ , KL ₂ , KL ₃ ... Indicator light, P ... Simultaneous drive control relay, N ₂ , N ₄ ... Simultaneous drive relay of simultaneous drive means, n ₂ , n ₄ ... Contact, U ₁ ... No. 1 display section,
U ₂ ...Second display section.

Claims (1)

[Claims] 1. A common terminal is connected to one side potential of an AC power source based on a command signal for alternating operation transmitted through a command signal line, and a pair of switching contacts are alternately connected each time the command signal is generated. an alternating switching device having a contact section for switching, a pair of dedicated lines connected to the pair of switching contacts of the alternating switching device via a diode, and a potential between the pair of dedicated lines and the other side of the AC power supply; a pair of control relays that are connected through diodes in the same direction as the diodes and control a pair of loads in response to half-wave currents on one side passing through these diodes; and a potential on the other side and the pair of dedicated lines. an operating contact connected between said diode and a diode opposite to said diode, and energizing said other side half-wave current to said pair of dedicated lines in response to operation of said pair of load control systems of said pair of control relays; , the pair of dedicated lines and the potential on one side are connected via a diode in the same direction as the diode connected to the operating contact, and the half-wave current on the other side is energized when the operating contact is turned on. a load monitoring control circuit having a display driving relay; a dedicated line other than the pair of dedicated lines; and a pair of abnormality detection contacts connected in parallel to each other so that only one of them operates. a pair of detection parts connected in series with a flickering contact in the AC power source and the other dedicated line via diodes facing oppositely to each other, and the other dedicated line and the AC A pair of receiving means are connected to the other side potential of the power source via diodes in opposite directions, and the output signals of the pair of receiving means are respectively inputted to determine whether each output signal is in an intermittent state or a continuous state. a pair of intermittent current discrimination circuits; a first display unit having a pair of indicator lights that respond to the intermittent discrimination output and continuous discrimination output of one of the intermittent current discrimination circuits; and an intermittent discrimination output of the other of the intermittent current discrimination circuits; a load abnormality display circuit having a second display section having an indicator light that responds to one of the output and the continuous discrimination output and a relay for simultaneous drive control that responds to the other; and a pair of alternating switching devices for the load monitoring control circuit. and a simultaneous drive means having a contact connected between the switching contacts of the simultaneous drive control relay, which responds to the output of the simultaneous drive control relay and stops when the command signal disappears.