3-2
Powering the Model 2221
FIGURE 3-1
Accessing Battery Compartment
The internal battery voltage is indicated by one of four LEDs
as described in the section “External DC Power Input” on
page 2-3. If no LED is illuminated, the battery voltage is less
than 5.5 Volts.
External Battery or DC Power
Note: The internal batteries need not
be present to operate the Model
2221 under external DC power.
The Model 2221 can be powered by an external 12 Volt
battery or an AC/DC adaptor providing a voltage within the
range 10.5 to 30 Vdc.
Note: The PSA017 115 Vac to 9Vdc
500 mA power adaptor provided
with the Model 2221 provides
approximately 12 Volts when lightly
loaded by the 65 mA drawn by the
2221.
Power will switch without interruption to the internal
batteries when there is an external power failure or if the
external voltage drops below the internal battery voltage.