SRS Labs SR560 - Manual (Page 20)

CIRCUIT DESCRIPTION
16
BATTERIES AND P.E.M.
The batteries used in the SR560 are of
sealed lead-acid construction. There are
three 12 V, 1.9 amp-hour batteries, two of
which serve as the positive power supply,
and one of which serves as the negative
power supply. Powering the SR560 alone,
battery life should be greater than 20 hours.
The batteries should last for more than 1000
charge / discharge cycles, provided the
guidelines under the Usage section are
followed. Two 3A, fast blow fuses on the
rear panel protect the battery supplies and
amplifier against excessive currents.
The power entry module (P.E.M.) contains
the AC line fuse, RFI filter, and voltage
selection card. To change the operating
voltage of the unit, the voltage selector
printed circuit card must be pulled out and
reinserted into the P.E.M. with the desired
operating voltage visible.
FRONT PANEL
The front panel contains the keypad
pushbuttons, LED indicators and serial shift
registers. The front panel pushbuttons are
decoded in a 3 x 4 matrix fashion. The front
panel LEDs are controlled by shift registers
U1 through U5, which allow the 5 eight-bit
control bytes to be serially shifted-in one bit
at a time. The red overload LED is
controlled directly from the output of the
overload comparator.
The battery LED is a dual-color LED that is
green when the unit is operating on battery
power, and turns red when the low_batt
signal is asserted.
The front panel output offset pot P1 is also
mounted on the front panel printed circuit
board.