The invention disclose a line breaking type antitheft alarm which comprises a
transformer, a rectifying circuit, a switch, a magnetically controlled switch, a
magnet, a
first light-emitting
diode, a second light-emitting
diode, a
relay, a time base integrated
chip, a four-tone warning
chip, a
voltage stabilizing tube, a
loudspeaker, a first
diode, a second diode, a third diode, a fourth diode, a fifth diode, a first
resistor, a second
resistor, a third
resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first
capacitor, a second
capacitor, a third
capacitor, a
triode and a battery. When the magnetically controlled switch is turned off, a power supply rapidly charges the second capacitor through the second resistor and a sixth diode, and
voltage of the trigger end of and
voltage of the reset locking end of a time base
integrated circuit also rise; when the voltage of the trigger end of and the voltage of the reset locking end are higher than a threshold value, the output end outputs a low level, a warning circuit works, and the
loudspeaker gives an alarm. The line breaking type warning is adopted, a line breaking type warning mode has a breakage-proof function, and the alarm can also be given even if a
signal line is destroyed; the line breaking type antitheft alarm is simple in circuit structure, adopted elements are fewer, so that the cost is low, and the line breaking type antitheft alarm is favorable for popularization.