Operation:  The LM 336 and 3K resistor provide a stable voltage of 2.5V at the inverted input of the

    LM311 which is a Comparator.  R2= 10K and R1 = 8.2K give the other input voltage which will be

    below 2.5 volts for a voltage of 4.5V or lower given by the battery.  The values of R2 and R1 can be

    adjusted accordingly for a higher or lower voltage alarm.  The 2.2uF capacitor may be used to remove

    any low voltage spikes present depending on the mechanism that is being powered by the battery.

    The Miniature Piezo Buzzer can be obtained at Radio Shack:  12V, PC Board Mount, part# 273-074,

    the LM 336 has a third pin which is not used for this application and can be broken off.