To provide the system with two well regulated voltages from the 9 volt battery, two
voltage regulators are used. The regulator A5 generates 5 volts while A6 produces 2.5
volts. The 2.5 volt supply is used to generate the mid-supply bias voltage used in the
signal processing circuits while the 5 volt supply is used in the alarm and the voltage
monitor circuits. Since the current demands of both supplies are very low, low power
regulators are used.