Voltage detector

Claim 2

A detector circuit for indicating the relationship of a monitored voltage to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a breakdown mode to establish at the offset junction an offset defined in proportion to the monitored voltage when the monitored voltage is above the lower level; a first resistor connected between a first signal junction and the second supply terminal for developing a first signal voltage thereacross at the first signal junction; a second resistor connected between a second signal junction and the second supply terminal for developing a second signal voltage thereacross at the second signal junction; a third resistor connected between the first signal junction and the first supply terminal for operating in conjunction with the first resistor to define the first signal voltage in proportion to the monitored voltage such that the difference between the first and second signal voltages is greater than a predetermined trigger potential when the monitored voltage is below the lower level; a fourth resistor connected between the second signal junction and the offset junction for operating in conjunction with the second resistor to define the second signal voltage in proportion to the offset voltage such that the difference between the first and second signal voltages is less than the trigger potential when the monitored voltage is between the lower level and the upper level; a control diode connected between the first signal junction and the offset junction for operating in a forward biased mode in conjunction with the first resistor to define the first signal voltage in proportion to the offset voltage such that the difference between the first and second signal voltages is greater than the trigger potential when the monitored voltage is above the upper level; and comparator means connected with the first and second signal junctions for producing a first output signal when the difference between the first and second signal voltages is greater than the trigger potential thereby to indicate that the monitored voltage is either below the lower level or above the upper level and for producing a second output signal when the difference between the first and second signal voltages is less than the trigger potential thereby to indicate that the monitored voltage is between the lower level and the upper level.

Claim 3

A detector circuit for indicating the relationship of a monitored voltage to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset voltage defined in proportion to the monitored voltage when the monitored voltage is above the lower level; a first resistor connected between a first signal junction and the second signal supply terminal for developing a first signal voltage thereacross at the first signal junction; a second resistor connected between a second signal junction and the second supply terminal for developing a second signal voltage thereacross at the second signal junction; switching means connected to the first and second signal junctions for shifting to a turned on condition when the difference between the first and second signal voltages is greater than a predetermined trigger potential and for shifting to a turned off condition when the difference between the first and second signal voltages is less than the predetermined trigger potential; a third resistor connected between the first signal junction and the first supply terminal for operating in conjunction with the first resistor to define the first signal voltage in proportion to the monitored voltage as determined by the voltage divider action of the first and third resistors such that the difference between the first and second signal voltages is greater than the trigger potential when the monitored voltage is below the lower level thereby to shift the switching means to the turned on cOndition; a fourth resistor connected between the second signal junction and the offset junction for operating in conjunction with the second resistor to define the second signal voltage in proportion to the offset voltage as determined by the voltage divider action of the second and fourth resistors such that the difference between the first and second signal voltages is less than the trigger potential when the monitored voltage is between the lower level and the upper level thereby to shift the switching means to the turned off condition; a control diode connected between the first signal junction and the offset junction for operating in a reverse biased mode to isolate the first signal junction from the offset junction when the offset voltage is less than the first signal voltage and for operating in a forward biased mode in conjunction with the first resistor to define the first signal voltage in proportion to the offset voltage when the offset voltage is greater than the first signal voltage such that the difference between the first and second signal voltages is greater than the trigger potential when the monitored voltage is above the upper level thereby to shift the switching means to the turned on condition; and an indicator device connected with the switching means for producing a first output signal when the switching means is in the turned on condition thereby to indicate that the monitored voltage is either blow the lower level or above the upper level and for producing a second output signal when the switching means is in the turned off condition thereby to indicate that the monitored voltage is between the lower level and the upper level.

Claim 4

A detector circuit for indicating the relationship of a monitored voltage to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset voltage defined in proportion to the monitored voltage when the monitored voltage is above the lower level; a first resistor connected between a first signal junction and the second signal supply terminal for developing a first signal voltage thereacross at the first signal junction; a second resistor connected between a second signal junction and the second supply terminal for developing a second signal voltage thereacross at the second signal junction; switching means connected to the first and second signal junctions for shifting to a turned on condition when the difference between the first and second signal voltages is greater than a predetermined trigger potential and for shifting to a turned off condition when the difference between the first and second signal voltages is less than the predetermined trigger potential; a third resistor connected between the first signal junction and the first supply terminal for operating in conjunction with the first resistor to define the first signal voltage in proportion to the monitored voltage as determined by the voltage divider action of the first and third resistors such that the difference between the first and second signal voltages is greater than the trigger potential when the monitored voltage is below the lower level thereby to shift the switching means to the turned on cOndition; a fourth resistor connected between the second signal junction and the offset junction for operating in conjunction with the second resistor to define the second signal voltage in proportion to the offset voltage as determined by the voltage divider action of the second and fourth resistors such that the difference between the first and second signal voltages is less than the trigger potential when the monitored voltage is between the lower level and the upper level thereby to shift the switching means to the turned off condition; a control diode connected between the first signal junction and the offset junction for operating in a reverse biased mode to isolate the first signal junction from the offset junction when the offset voltage is less than the first signal voltage and for operating in a forward biased mode in conjunction with the first resistor to define the first signal voltage in proportion to the offset voltage when the offset voltage is greater than the first signal voltage such that the difference between the first and second signal voltages is greater than the trigger potential when the monitored voltage is above the upper level thereby to shift the switching means to the turned on condition; and an indicator device connected with the switching means for producing a first output signal when the switching means is in the turned on condition thereby to indicate that the monitored voltage is either blow the lower level or above the upper level and for producing a second output signal when the switching means is in the turned off condition thereby to indicate that the monitored voltage is between the lower level and the upper level.

Claim 5

A detector circuit for indicating the relative magnitude of a monitored voltage with respect to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the magnitude of the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset junction having a magnitude determined in proportion to the magnitude of the monitored voltage when the magnitude of the monitored voltage is above the lower level; a first resistor connected between a first signal junction and the second supply terminal for developing a first signal voltage thereacross at the first signal junction; a second resistor connected between a second signal junction and the second supply terminal for developing a second signal voltage at the second signal junction; switching means connected to the first and second signal junctions for shifting to a turned on condition when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than a predetermined trigger potential and for shifting to a turned off condition when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the predetermined trigger potential; a third resistor connected between the first signal junction and the first supply terminal for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the monitored voltage as primarily determined by the voltage divider action of the first and third resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is below the lower level thereby to shift the switching means to the turned on condition; a fourth resistor connected between the second signal junction and the offset junction for operating in series relationship with the second resistor to define the magnitude of the second signaL voltage in proportion to the magnitude of the offset voltage as primarily determined by the voltage divider action of the second and fourth resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the trigger potential when the magnitude of the monitored voltage is between the lower level and the upper level thereby to shift the switching means to the turned off condition; a control diode and a fifth resistor connected in series between the first signal junction and the offset junction, the control diode operating in a reverse biased mode to isolate the first signal junction from the offset junction when the offset voltage is less than the first signal voltage and for operating in a forward biased mode to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage when the offset voltage is greater than the first signal voltage, the fifth resistor operating in series relationship with the first resistor when the control diode is forward biased to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the voltage divider action of the first and fifth resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is above the upper level thereby to shift the switching means to the turned on condition; and an indicator device connected with the switching means for producing a first output signal when the switching means is in the turned on condition thereby to indicate that the magnitude of the monitored voltage is either below the lower level or above the upper level and for producing a second output signal when the switching means is in the turned off condition thereby to indicate that the magnitude of the monitored voltage is between the lower level and the upper level.

Claim 6

A detector circuit for indicating the relative magnitude of a monitored voltage with respect to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the magnitude of the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset junction having a magnitude determined in proportion to the magnitude of the monitored voltage when the magnitude of the monitored voltage is above the lower level; a first resistor connected between a first signal junction and the second supply terminal for developing a first signal voltage thereacross at the first signal junction; a second resistor connected between a second signal junction and the second supply terminal for developing a second signal voltage at the second signal junction; switching means connected to the first and second signal junctions for shifting to a turned on condition when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than a predetermined trigger potential and for shifting to a turned off condition when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the predetermined trigger potential; a third resistor connected between the first signal junction and the first supply terminal for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the monitored voltage as primarily determined by the voltage divider action of the first and third resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is below the lower level thereby to shift the switching means to the turned on condition; a fourth resistor connected between the second signal junction and the offset junction for operating in series relationship with the second resistor to define the magnitude of the second signaL voltage in proportion to the magnitude of the offset voltage as primarily determined by the voltage divider action of the second and fourth resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the trigger potential when the magnitude of the monitored voltage is between the lower level and the upper level thereby to shift the switching means to the turned off condition; a control diode and a fifth resistor connected in series between the first signal junction and the offset junction, the control diode operating in a reverse biased mode to isolate the first signal junction from the offset junction when the offset voltage is less than the first signal voltage and for operating in a forward biased mode to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage when the offset voltage is greater than the first signal voltage, the fifth resistor operating in series relationship with the first resistor when the control diode is forward biased to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the voltage divider action of the first and fifth resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is above the upper level thereby to shift the switching means to the turned on condition; and an indicator device connected with the switching means for producing a first output signal when the switching means is in the turned on condition thereby to indicate that the magnitude of the monitored voltage is either below the lower level or above the upper level and for producing a second output signal when the switching means is in the turned off condition thereby to indicate that the magnitude of the monitored voltage is between the lower level and the upper level.

Claim 7

A detector circuit for indicating the relative magnitude of a monitored voltage with respect to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the magnitude of the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset voltage having a magnitude defined in proportion to the magnitude of the monitored voltage when the magnitude of the monitored voltage is above the lower level; a first resistor connected between a first signal junction and the second supply terminal for developing a first signal voltage thereacross at the first signal junction; a second resistor connected between a second signal junction and the second supply terminal for developing a second signal voltage at the second signal junction; first and second transistors of opposite conductivity type each switchable between a fully conductive state and a fully nonconductive state; means connecting the first transistor with the first and second signal junctions such that the first transistor is switched to the fully conductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than a predetermined trigger potential and such that the first transistor is switched to the fully nonconductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the predetermined trigger potential; means connecting the second transistor with the first transistor such that the second transistor is switched to the fully conductive state as the first transistor is switched to the fully conductive state and such that the second transiStor is switched to the fully nonconductive state as the first transistor is switched to the fully nonconductive state; a third resistor connected between a first signal junction and the first supply terminal for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the monitored voltage as primarily determined by the resistance ratio of the first resistor to the third resistor such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is below the lower level thereby to switch the first and second transistors to the fully conductive state; a fourth resistor connected between the second signal junction and the offset junction for operating in series relationship with the second resistor to define the magnitude of the second signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the resistance ratio of the second resistor to the fourth resistor such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the trigger potential when the magnitude of the monitored voltage is between the lower level and the upper level thereby to switch the first and second transistors to the fully nonconductive state; a control diode and a fifth resistor connected in series relationship between the first signal junction and the offset junction, the control diode operating in a reverse biased mode to isolate the first signal junction from the offset junction when the offset voltage is less than the first signal voltage and for operating in a forward biased mode to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage when the offset voltage is greater than the first signal voltage, the fifth resistor operating in series relationship with the first resistor when the control diode is forward biased to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the resistance ratio of the first resistor to the fifth resistor which resistance ratio is greater than the resistance ratio of the second resistor to the fourth resistor such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is above the upper level thereby to switch the first and second transistors to the fully conductive state; and an indicator device connected with the second transistor for producing a first output signal when the second transistor is in the fully conductive state thereby to indicate that the magnitude of the monitored voltage is either below the lower level or above the upper level and for producing a second output signal when the second transistor is in the fully nonconductive state thereby to indicate that the magnitude of the monitored voltage is between the lower level and the upper level.

Claim 8

A detector circuit for indicating the relative magnitude of a monitored voltage with respect to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the magnitude of the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset voltage having a magnitude defined in proportion to the magnitude of the monitored voltage when the magnitude of the monitored voltage is above the lower level; a first resistor connected between a first signal junction and the second supply terminal for developing a first signal voltage thereacross at the first signal junction; a second resistor connected between a second signal junction and the second supply terminal for developing a second signal voltage at the second signal junction; first and second transistors of opposite conductivity type each switchable between a fully conductive state and a fully nonconductive state; means connecting the first transistor with the first and second signal junctions such that the first transistor is switched to the fully conductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than a predetermined trigger potential and such that the first transistor is switched to the fully nonconductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the predetermined trigger potential; means connecting the second transistor with the first transistor such that the second transistor is switched to the fully conductive state as the first transistor is switched to the fully conductive state and such that the second transiStor is switched to the fully nonconductive state as the first transistor is switched to the fully nonconductive state; a third resistor connected between a first signal junction and the first supply terminal for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the monitored voltage as primarily determined by the resistance ratio of the first resistor to the third resistor such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is below the lower level thereby to switch the first and second transistors to the fully conductive state; a fourth resistor connected between the second signal junction and the offset junction for operating in series relationship with the second resistor to define the magnitude of the second signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the resistance ratio of the second resistor to the fourth resistor such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the trigger potential when the magnitude of the monitored voltage is between the lower level and the upper level thereby to switch the first and second transistors to the fully nonconductive state; a control diode and a fifth resistor connected in series relationship between the first signal junction and the offset junction, the control diode operating in a reverse biased mode to isolate the first signal junction from the offset junction when the offset voltage is less than the first signal voltage and for operating in a forward biased mode to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage when the offset voltage is greater than the first signal voltage, the fifth resistor operating in series relationship with the first resistor when the control diode is forward biased to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the resistance ratio of the first resistor to the fifth resistor which resistance ratio is greater than the resistance ratio of the second resistor to the fourth resistor such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is above the upper level thereby to switch the first and second transistors to the fully conductive state; and an indicator device connected with the second transistor for producing a first output signal when the second transistor is in the fully conductive state thereby to indicate that the magnitude of the monitored voltage is either below the lower level or above the upper level and for producing a second output signal when the second transistor is in the fully nonconductive state thereby to indicate that the magnitude of the monitored voltage is between the lower level and the upper level.

Claim 9

A detector circuit for indicating the relative magnitude of a monitored voltage with respect to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the magnitude of the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset voltage having a magnitude defined in proportion to the magnitude of the monitored voltage when the magnitude of the monitored voltage is above the lower level; means connected between a first signal junction and the second supply terminal and including a first resistor for deveLoping a first signal voltage thereacross at the first signal junction; means connected between a second signal junction and the second supply terminal and including a second resistor having a resistance of the same order of magnitude as but less than the resistance of the first resistor for developing a second signal voltage at the second signal junction; first and second transistors of opposite conductivity type each having base, emitter and collector electrodes and each operable between a fully conductive state and a fully nonconductive state; means for connecting the base electrode of the first transistor to the first signal junction and for connecting the emitter electrode of the first transistor to the second signal junction such that the first transistor switches toward the fully conductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than a predetermined trigger potential and such that the first transistor switches toward the fully nonconductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the predetermined trigger potential; means for connecting the base electrode of the first transistor to the collector electrode of the second transistor and for connecting the emitter electrode of the second transistor to the first supply terminal and for connecting the collector electrode of the second transistor to an output junction such that the second transistor switches toward the fully conductive state as the first transistor switches toward the fully conductive state and such that the second transistor switches toward the fully nonconductive state as the first transistor switches toward the fully nonconductive state; a feedback resistor connected between the output junction and the first signal junction for increasing the magnitude of the bias voltage as the second transistor switches toward the fully conductive state thereby to accelerate the switching of the first and second transistors to the fully conductive state and for decreasing the magnitude of the first signal voltage as the second transistor switches toward the fully nonconductive state thereby to accelerate the switching of the first and second transistors to the fully nonconductive state; means connected between the first signal junction and the first supply terminal and including a third resistor having a resistance several orders of magnitude greater than the resistance of the first resistor for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the monitored voltage as primarily determined by the voltage divider action of the first and third resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is below the lower level thereby to switch the first and second transistors to the fully conductive state; means connected between the second signal junction and the offset junction and including a fourth resistor having a resistance of the same order of magnitude as but greater than the second resistor for operating in series relationship with the second resistor to define the magnitude of the second signal voltage in proportion to the magnitude of the offset voltage such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the trigger potential when the magnitude of the monitored voltage is between the upper level and the lower level thereby to switch the first and second transistors to the fully nonconductive state; means connected between the first signal junction and the offset junction and including a control diode for operating in a forward biased mode to isolate the first signal junction from the offset junction when The offset voltage is less than the first signal voltage and for operating in a forward biased mode to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage when the offset voltage is greater than the first signal voltage, the means further including a fifth resistor having a resistance of the same order of magnitude as but less than the first resistor and several orders of magnitude less than the third resistor for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the voltage divider action of the first and fifth resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is above the upper level thereby to switch the first and second transistors to the fully conductive state; and an indicator device connected between the output junction and the second supply terminal for producing a first output signal when the second transistor is in the fully conductive state thereby to indicate that the magnitude of the monitored voltage is either below the lower level or above the upper level and for producing a second output signal when the second transistor is in the fully nonconductive state thereby to indicate that the magnitude of the monitored voltage is between the lower level and the upper level.

Claim 10

A detector circuit for indicating the relative magnitude of a monitored voltage with respect to an upper level and a lower level where the monitored voltage appears between first and second supply terminals, comprising: a Zener diode connected between the first supply terminal and an offset junction for operating in a pre-breakdown mode to isolate the offset junction from the first supply terminal when the magnitude of the monitored voltage is below the lower level and for operating in a breakdown mode to establish at the offset junction an offset voltage having a magnitude defined in proportion to the magnitude of the monitored voltage when the magnitude of the monitored voltage is above the lower level; means connected between a first signal junction and the second supply terminal and including a first resistor for deveLoping a first signal voltage thereacross at the first signal junction; means connected between a second signal junction and the second supply terminal and including a second resistor having a resistance of the same order of magnitude as but less than the resistance of the first resistor for developing a second signal voltage at the second signal junction; first and second transistors of opposite conductivity type each having base, emitter and collector electrodes and each operable between a fully conductive state and a fully nonconductive state; means for connecting the base electrode of the first transistor to the first signal junction and for connecting the emitter electrode of the first transistor to the second signal junction such that the first transistor switches toward the fully conductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than a predetermined trigger potential and such that the first transistor switches toward the fully nonconductive state when the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the predetermined trigger potential; means for connecting the base electrode of the first transistor to the collector electrode of the second transistor and for connecting the emitter electrode of the second transistor to the first supply terminal and for connecting the collector electrode of the second transistor to an output junction such that the second transistor switches toward the fully conductive state as the first transistor switches toward the fully conductive state and such that the second transistor switches toward the fully nonconductive state as the first transistor switches toward the fully nonconductive state; a feedback resistor connected between the output junction and the first signal junction for increasing the magnitude of the bias voltage as the second transistor switches toward the fully conductive state thereby to accelerate the switching of the first and second transistors to the fully conductive state and for decreasing the magnitude of the first signal voltage as the second transistor switches toward the fully nonconductive state thereby to accelerate the switching of the first and second transistors to the fully nonconductive state; means connected between the first signal junction and the first supply terminal and including a third resistor having a resistance several orders of magnitude greater than the resistance of the first resistor for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the monitored voltage as primarily determined by the voltage divider action of the first and third resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is below the lower level thereby to switch the first and second transistors to the fully conductive state; means connected between the second signal junction and the offset junction and including a fourth resistor having a resistance of the same order of magnitude as but greater than the second resistor for operating in series relationship with the second resistor to define the magnitude of the second signal voltage in proportion to the magnitude of the offset voltage such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is less than the trigger potential when the magnitude of the monitored voltage is between the upper level and the lower level thereby to switch the first and second transistors to the fully nonconductive state; means connected between the first signal junction and the offset junction and including a control diode for operating in a forward biased mode to isolate the first signal junction from the offset junction when The offset voltage is less than the first signal voltage and for operating in a forward biased mode to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage when the offset voltage is greater than the first signal voltage, the means further including a fifth resistor having a resistance of the same order of magnitude as but less than the first resistor and several orders of magnitude less than the third resistor for operating in series relationship with the first resistor to define the magnitude of the first signal voltage in proportion to the magnitude of the offset voltage as primarily determined by the voltage divider action of the first and fifth resistors such that the difference between the magnitude of the first signal voltage and the magnitude of the second signal voltage is greater than the trigger potential when the magnitude of the monitored voltage is above the upper level thereby to switch the first and second transistors to the fully conductive state; and an indicator device connected between the output junction and the second supply terminal for producing a first output signal when the second transistor is in the fully conductive state thereby to indicate that the magnitude of the monitored voltage is either below the lower level or above the upper level and for producing a second output signal when the second transistor is in the fully nonconductive state thereby to indicate that the magnitude of the monitored voltage is between the lower level and the upper level.