NELLCOR PURITAN BENNETT Symphony N-3000 Service Manual page 102

Technical Supplement
S- 12
Timer U21 also switches the backup battery power from U20 to RAMs U13
and U23, the processor/power fail circuitry, when the +5V supply is below its
lower limit.
Processor/Power Fail Circuitry — This circuitry sounds the piezo speaker
if the processor fails to operate or the 5V power unexpectedly falls below its
lower regulation limit.
e. Connectors
This section describes UIF connectors and pinouts other than the docking
connector J13.
J8 — J8 is a 40-pin daughter board connector that interfaces the UIF module
to the communications board. This board uses only the first 16 pins on the
connector.