Low battery indicator circuit project

Very simple low battery indicator schematic is based on two transistors . The led connected in this circuit will flash when the voltage is low ( bellow 5 volts ) . The circuit consumption is very low ( about 25 micro amps ) when the led is not flashing .

When the battery voltage it drops below 5 volts the base voltage drops to 2.5 volts and the emitter can reach a voltage sufficient to turn on the PNP and the NPN also conducts dropping the voltage across the circuit even more and the circuit snaps on. When the 4.7 uF capacitor has discharged , the led is not flashing and the capacitor begins charging again . The zenner diode from this circuit must be a 4,7 volts zenner .