referring to fig2 the circuit diagram of the circuit for indicating abnormality of a three - mode surge absorber of a public electric power in the preferred embodiment of the present invention is illustrated . the circuit of the present invention includes a first two - end fuse f 1 , a first surge absorbing device 40 , a second surge absorbing device 50 , an abnormal indication circuit 60 , and a second two - end fuse f 2 . the first surge absorbing device 40 has a two - end temperature sensing fuse 401 and a metal oxide varistor 402 . the second surge absorbing device 50 includes a surge absorbing device 501 , the first end thereof is coupled to a line output end , and the second end is coupled to the abnormal indication circuit 60 . the first end of the second surge absorbing device 502 is coupled to a line input end , and the second end thereof is coupled to the abnormal indication circuit 60 . the two - end temperature sensing fuse 503 has a first end coupled to the second ends of the first and second surge absorbing devices 501 and 502 , and has a second end coupled to the first end of the second two - end fuse f 2 . the abnormal indication circuit 60 has a diode d 3 . the anode thereof is coupled to a first surge absorbing device 40 . a second end of a first resistor r 1 is coupled to the cathode of the diode d 3 . a second resistor r 2 has a first end coupled to a second end of the first resistor r 2 , and the second surge absorbing device 50 ( point a in fig2 ). a first transistor q 1 has a base coupled to the second end of the second resistor r 2 , and the emitter thereof is coupled to the ground input end . a third resistor r 3 has a first end coupled to the cathode of the diode d 3 . a fourth resistor r 4 has a first end coupled to the first resistor r 1 , the third resistor r 3 , and the cathode of the diode d 3 , and the second end thereof is coupled to the collector of the first transistor q 1 ( point b in fig2 ). a fifth resistor r 5 has a first end coupled to a second end of the fourth resistor r 4 and the collector of the first transistor q 1 . a second transistor q 2 has a base coupled to a second end of the fifth resistor r 5 , and the collector thereof is coupled to the second end of the third resistor r 3 . a light emitting diode d 4 has a anode coupled to the emitter the second transistor q 2 , and the cathode thereof is coupled to the neutral output end . a zener diode z 1 has a cathode coupled to the collector of the second transistor q 2 , and the anode thereof is coupled to the neutral output end for supplying a rated voltage . the circuit property for the circuit for indicating abnormality of a three - mode surge absorber of a public electric power according to the present invention may be analyzed by the following two modes ( 1 ) the transient / surge absorber is heated and then is destroyed gradually , and ( 2 ) the transient / surge absorber is subjected to a high voltage instantly and then is destroyed . in the following , the properties of these two modes are analyzed . a ) l - n mode : the metal oxide varistor 402 is abnormal , and is heated , since it tightly resists against the two - end temperature sensing fuse 401 . finally , the temperature of the metal oxide varistor 402 will burn - cut two - end temperature sensing fuse 401 . therefore , the surge protection indicator d 4 has no current and then extinguishes . b ) l - g mode : the metal oxide varistor 502 has abnormality and then heat gradually , since it resists tightly against the two - end temperature sensing fuse 503 , when the two - end temperature sensing fuse 503 is burn - cut so that point a is in a floating condition . when the transistor is conductive , point b is grounded so that transistor q 2 is turned off and the surge protection indicator d 4 extinguishes due to no current flowing therethrough . c ) n - g mode : the metal oxide varistor 501 has abnormality and heats gradually . since it resists tightly against the two - end temperature sensing fuse 503 , when the two - end temperature sensing fuse 503 is burn - cut so that point a is in a floating condition . when the transistor is conductive , point b is grounded so that transistor q 2 is turned off and the surge protection indicator d 4 extinguishes due to no current flowing therethrough . ( 2 ) the transient / surge absorber is subjected to a high voltage instantly and then is destroyed . a ) l - n mode : when abnormality occurs , and high voltage retains , the metal oxide varistor 402 will short - circuit instantly . since a large current flows into the fuse f 1 so that the fuse f 1 is heated instantly and then burn - cut . other than cutting off the current path of the metal oxide varistor 402 , the path of the surge protection indicator d 4 is also cut off so that the surge protection indicator d 4 extinguishes . b ) l - g mode : when abnormality occurs , and high voltage retains , the metal oxide varistor 502 will short - circuit instantly . since a large current flows into the fuses f 1 and f 2 , and thus in design , f 2 has a smaller current path ( or f 2 has a small turn - off current than that of f 1 ), so that the fuse f 2 is heated instantly and then burn - cut . the current path of the metal oxide varistor 502 is cut off so that point a is in a floating condition and transistor q 1 is conductive , point b is grounded so . that transistor q 2 is turned off . the surge protection indicator d 4 extinguishes due to no current flowing therethrough . c ) n - g mode : when abnormality occurs , and high voltage retains , the metal oxide varistor 501 will short - circuit instantly . since a large current flows into the fuse f 2 , so that the fuse f 2 is heated instantly and then burn - cut . the current path of the metal oxide varistor 503 is cut off so that point a is in a floating condition and transistor q 1 is conductive , point b is grounded so that transistor q 2 is turned off . the surge protection indicator d 4 extinguishes due to no current flowing therethrough . in summary , other than indicating the abnormalities of the l - n , l - g , n - g surge absorbing devices , the circuit for indicating abnormality of a three - mode surge absorber of a public electric power according to the present invention assure that no leakage occurs as it is destroyed in all modes . besides , herein , the metal oxide varistor is taken as an example of the first and second surge absorbing devices of the present invention , however , the surge absorbing device , such as a gas tube , a transient voltage suppressor or sidactor , etc . serves in the present invention . especially , the three - end fuses 50 and 80 are not limited to a structure of three ends , it is only for the sake of convenience . the present invention is thus described , it will be obvious that the same may be varied in many ways . such variations are not to be regarded as a departure from the spirit and scope of the present invention , and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims .