Smiths Medical BCI 3304, Service Manual

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Chapter 2: Oximeter Circuit Description
3304 Service Manual 2-9
SIgnAL DeSCRIPTIOn
STBY Input signal indicating that I/O key was pressed.
TXA0,
RXA0
Asynchronous serial communication signals used to control
external optional printer.
TXA1,
RXA1
Asynchronous serial communication signals used for production
testing.
TXS TXS is the microprocessor’s high-speed, synchronous serial
output transmitted data signal.
V-AMB V-AMB is the output of the front-end differential amplifier.
V-BATT Signal used to monitor battery voltage.
V-POWER Input external voltage. Also used to light green “CHARGE” LED
on the display board
V-RAM +5 VDC voltage generated by U26 to power RAM and on-off
circuitry.
V-REF 2.500 VDC reference voltage.
VCC VCC is the reg5 VDC supply generated by +5 volt power
supply regulator chip U26 and its discrete components.
VDD Same as VCC.
VSS Digital ground.
WDT Watch dog timer input signal, resets watch dog timer.