NELLCOR PURITAN BENNETT Symphony N-3000 Service Manual page 108

Technical Supplement
S- 18
Selecting RS232 serial signaling is accomplished by moving switches
S1,S3,S5,S7 on SW1 and SW2 to the on position and switches S2,S4,S6,S8 to
the OFF position. This enables U9 and disables U10. With RS232 selected, J1
has the following pinout:
1 DTR
2 DSR
3 TXD
4 GND
5 RXD
6 Nurse Call/3.3V
Selecting RS422 serial signaling is accomplished by moving switches
S2,S4,S6,S8 on SW1 and SW2 to the on position and switches S1,S3,S5,S7 to
the OFF position. This enables U10 and disables U9. With RS422 selected, J1
has the following pinout:
1 TXD-
2 RXD-
3 TXD
4 GND
5 RXD
6 Nurse Call/3.3V
b. Alarm Active/3.3V Power
Isolated alarm active or 3.3 volt power is selectable as a 500mA fused output
on J1 Pin 6. Placing switch block SW3, S1 to the on position, and S2,S3,S4 to
the OFF position, will select the alarm active signal on J1 Pin 6. The alarm
active signal provided is a normally open relay that shorts Pin 6, J1 to Pin 4,
J1 signaling an alarm event.
To select isolated 3.3 volt power, place switch SW3 S1 to the OFF position
and S2,S3,S4 to the on position. This provides up to 100mA of 3.3 volt power.